Binary Search Tree - CompareTo Error

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  • BenCoo
    #1

    Binary Search Tree - CompareTo Error

    Hello,

    In a Binary Search Tree I get the error : Object must be of type String

    if I run the form only with the "Dim bstLidnummer As New BinarySearchTre e"
    it works fine.

    Thanks for any help on this,

    Benny

    My BST-code lookes lokes this :
    *************** *************** *************** *****
    Class BST
    *************** *************** *************** *****
    Public Class BinarySearchTre e
    Private Class TreeNode
    Private mData As IComparable
    Private mLeftNode As TreeNode
    Private mRightNode As TreeNode

    Public Sub New(ByVal data As IComparable)
    Me.mData = data
    End Sub

    Public ReadOnly Property Data() As IComparable
    Get
    Return Me.mData
    End Get
    End Property

    Public Property LeftNode() As TreeNode
    Get
    Return Me.mLeftNode
    End Get
    Set(ByVal value As TreeNode)
    Me.mLeftNode = value
    End Set
    End Property

    Public Property RightNode() As TreeNode
    Get
    Return Me.mRightNode
    End Get
    Set(ByVal value As TreeNode)
    Me.mRightNode = value
    End Set
    End Property

    Public Sub Add(ByVal data As IComparable)
    If data.CompareTo( Me.mData) <= 0 Then
    If Me.mLeftNode Is Nothing Then
    Me.mLeftNode = New TreeNode(data)
    Else
    Me.mLeftNode.Ad d(data)
    End If
    Else
    If Me.mRightNode Is Nothing Then
    Me.mRightNode = New TreeNode(data)
    Else
    Me.mRightNode.A dd(data)
    End If
    End If
    End Sub
    End Class

    Private mRoot As TreeNode

    Public Sub Add(ByVal data As IComparable)
    If mRoot Is Nothing Then
    mRoot = New TreeNode(data)
    Else
    mRoot.Add(data)
    End If
    End Sub

    Public Function Search(ByVal data As IComparable) As Object
    Return Me.Search(data, Me.mRoot)
    End Function

    Private Function Search(ByVal data As IComparable, ByVal node As
    TreeNode) As Object

    If node Is Nothing Then
    Return Nothing
    Else
    Dim result As Integer = data.CompareTo( node.Data) '****** this is
    the error I get on this line :Object must be of type String.

    If result = 0 Then
    Return node.Data
    ElseIf result < 0 Then
    Return Me.Search(data, node.LeftNode)
    Else
    Return Me.Search(data, node.RightNode)
    End If
    End If

    End Function
    End Class
    *************** **************
    The class Person
    *************** **************
    Public Class Persoon
    Inherits BusinessObject
    Implements IComparable

    Private mVnaam As String
    Private mAnaam As String

    Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
    Me.mVnaam = Vnaam
    Me.mAnaam = Anaam
    End Sub

    Public Property Vnaam() As String
    Get
    Return Me.mVnaam
    End Get
    Set(ByVal value As String)
    mVnaam = value
    End Set
    End Property

    Public Property Anaam() As String
    Get
    Return Me.mAnaam
    End Get
    Set(ByVal value As String)
    Me.mAnaam = value
    End Set
    End Property

    Public Overrides Function IsValid() As Boolean
    If Me.isValidVnaam () And Me.isValidAnaam () Then
    Return True
    Else
    Return False
    End If
    End Function

    Private Function isValidVnaam() As Boolean
    If Me.Vnaam.Trim.L ength 0 Then
    Return True
    Else
    Return False
    End If
    End Function

    Private Function isValidAnaam() As Boolean
    If Me.Anaam.Trim.L ength 0 Then
    Return True
    Else
    Return False
    End If
    End Function

    Public Overloads Function CompareTo(ByVal obj As Object) As Integer
    Implements System.ICompara ble.CompareTo
    Return Me.mVnaam.Compa reTo(CType(obj, Persoon).Vnaam)
    End Function
    End Class
    *************** *************** ****
    The Form :
    *************** *************** ****
    Public Class frmBinarySearch Tree

    Private Sub btnExecute_Clic k(ByVal sender As System.Object, ByVal e As
    System.EventArg s) Handles btnExecute.Clic k
    Dim bstLedenLijst As New BinarySearchTre e
    Dim bstLidnummer As New BinarySearchTre e
    Dim txtOutput As String = ""

    bstLidnummer.Ad d("5")
    bstLidnummer.Ad d("2")
    bstLidnummer.Ad d("1")
    bstLidnummer.Ad d("4")
    bstLidnummer.Ad d("3")
    txtOutput = bstLidnummer.Se arch("3") & vbCrLf

    bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
    bstLedenLijst.A dd(New Persoon("Jamie-Lee", "Curtis"))
    bstLedenLijst.A dd(New Persoon("Demi", "Moore"))
    bstLedenLijst.A dd(New Persoon("Julia" , "Roberts"))
    bstLedenLijst.A dd(New Persoon("Andie" , "MacDowell" ))

    txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf

    Me.txtOutput.Te xt = txtOutput

    End Sub

    Private Sub btnExit_Click(B yVal sender As System.Object, ByVal e As
    System.EventArg s) Handles btnExit.Click
    Application.Exi t()
    End Sub

    End Class



    Tags: None
    • Jay B. Harlow
      #2
      Re: Binary Search Tree - CompareTo Error

      BenCoo,
      Interesting homework assignment; I miss those days...

      Anyway to answer your question:
      Dim bstLedenLijst As New BinarySearchTre e
      Dim bstLidnummer As New BinarySearchTre e
      Dim txtOutput As String = ""
      >
      bstLidnummer.Ad d("5")
      txtOutput = bstLidnummer.Se arch("3") & vbCrLf
      >
      bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
      >
      txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
      Ah! There's the Rub!

      bstLedenLijst contains a collection of Persoon objects, you are attempting
      to compare Persoon objects to a String object! You need to pass a Persoon
      object to bstLedenLijst.S earch. I would recommend you change
      BinarySearchTre e to a Generic class; changing this obscure runtime error
      into an obvious compile time error!

      Something like:

      Public Class BinarySearchTre e(Of T As IComparable)

      Private Class TreeNode
      Private mData As T
      Private mLeftNode As TreeNode
      Private mRightNode As TreeNode

      Public Sub New(ByVal data As T)
      Me.mData = data
      End Sub

      Public ReadOnly Property Data() As T
      Get
      Return Me.mData
      End Get
      End Property

      Public Property LeftNode() As TreeNode
      Get
      Return Me.mLeftNode
      End Get
      Set(ByVal value As TreeNode)
      Me.mLeftNode = value
      End Set
      End Property

      Public Property RightNode() As TreeNode
      Get
      Return Me.mRightNode
      End Get
      Set(ByVal value As TreeNode)
      Me.mRightNode = value
      End Set
      End Property

      Public Sub Add(ByVal data As T)
      If data.CompareTo( Me.mData) <= 0 Then
      If Me.mLeftNode Is Nothing Then
      Me.mLeftNode = New TreeNode(data)
      Else
      Me.mLeftNode.Ad d(data)
      End If
      Else
      If Me.mRightNode Is Nothing Then
      Me.mRightNode = New TreeNode(data)
      Else
      Me.mRightNode.A dd(data)
      End If
      End If
      End Sub
      End Class

      Private mRoot As TreeNode

      Public Sub Add(ByVal data As T)
      If mRoot Is Nothing Then
      mRoot = New TreeNode(data)
      Else
      mRoot.Add(data)
      End If
      End Sub

      Public Function Search(ByVal data As T) As Object
      Return Me.Search(data, Me.mRoot)
      End Function

      Private Function Search(ByVal data As T, ByVal node As TreeNode) As
      Object

      If node Is Nothing Then
      Return Nothing
      Else
      Dim result As Integer = data.CompareTo( node.Data) '****** this
      is the error I get on this line :Object must be of type String.

      If result = 0 Then
      Return node.Data
      ElseIf result < 0 Then
      Return Me.Search(data, node.LeftNode)
      Else
      Return Me.Search(data, node.RightNode)
      End If
      End If

      End Function
      End Class

      Then when you define your trees, you give the type of tree they are!
      Dim bstLedenLijst As New BinarySearchTre e(Of String)
      Dim bstLidnummer As New BinarySearchTre e(Of Persoon)
      NOTE: You need VS 2005 for generics.

      --
      Hope this helps
      Jay B. Harlow
      ..NET Application Architect, Enthusiast, & Evangelist
      T.S. Bradley - http://www.tsbradley.net


      "BenCoo" <teddyb58@hotma il.comwrote in message
      news:CNPkh.2608 24$tk1.5394486@ phobos.telenet-ops.be...
      Hello,
      >
      In a Binary Search Tree I get the error : Object must be of type String
      >
      if I run the form only with the "Dim bstLidnummer As New
      BinarySearchTre e"
      it works fine.
      >
      Thanks for any help on this,
      >
      Benny
      >
      My BST-code lookes lokes this :
      *************** *************** *************** *****
      Class BST
      *************** *************** *************** *****
      Public Class BinarySearchTre e
      Private Class TreeNode
      Private mData As IComparable
      Private mLeftNode As TreeNode
      Private mRightNode As TreeNode
      >
      Public Sub New(ByVal data As IComparable)
      Me.mData = data
      End Sub
      >
      Public ReadOnly Property Data() As IComparable
      Get
      Return Me.mData
      End Get
      End Property
      >
      Public Property LeftNode() As TreeNode
      Get
      Return Me.mLeftNode
      End Get
      Set(ByVal value As TreeNode)
      Me.mLeftNode = value
      End Set
      End Property
      >
      Public Property RightNode() As TreeNode
      Get
      Return Me.mRightNode
      End Get
      Set(ByVal value As TreeNode)
      Me.mRightNode = value
      End Set
      End Property
      >
      Public Sub Add(ByVal data As IComparable)
      If data.CompareTo( Me.mData) <= 0 Then
      If Me.mLeftNode Is Nothing Then
      Me.mLeftNode = New TreeNode(data)
      Else
      Me.mLeftNode.Ad d(data)
      End If
      Else
      If Me.mRightNode Is Nothing Then
      Me.mRightNode = New TreeNode(data)
      Else
      Me.mRightNode.A dd(data)
      End If
      End If
      End Sub
      End Class
      >
      Private mRoot As TreeNode
      >
      Public Sub Add(ByVal data As IComparable)
      If mRoot Is Nothing Then
      mRoot = New TreeNode(data)
      Else
      mRoot.Add(data)
      End If
      End Sub
      >
      Public Function Search(ByVal data As IComparable) As Object
      Return Me.Search(data, Me.mRoot)
      End Function
      >
      Private Function Search(ByVal data As IComparable, ByVal node As
      TreeNode) As Object
      >
      If node Is Nothing Then
      Return Nothing
      Else
      Dim result As Integer = data.CompareTo( node.Data) '****** this is
      the error I get on this line :Object must be of type String.
      >
      If result = 0 Then
      Return node.Data
      ElseIf result < 0 Then
      Return Me.Search(data, node.LeftNode)
      Else
      Return Me.Search(data, node.RightNode)
      End If
      End If
      >
      End Function
      End Class
      *************** **************
      The class Person
      *************** **************
      Public Class Persoon
      Inherits BusinessObject
      Implements IComparable
      >
      Private mVnaam As String
      Private mAnaam As String
      >
      Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
      Me.mVnaam = Vnaam
      Me.mAnaam = Anaam
      End Sub
      >
      Public Property Vnaam() As String
      Get
      Return Me.mVnaam
      End Get
      Set(ByVal value As String)
      mVnaam = value
      End Set
      End Property
      >
      Public Property Anaam() As String
      Get
      Return Me.mAnaam
      End Get
      Set(ByVal value As String)
      Me.mAnaam = value
      End Set
      End Property
      >
      Public Overrides Function IsValid() As Boolean
      If Me.isValidVnaam () And Me.isValidAnaam () Then
      Return True
      Else
      Return False
      End If
      End Function
      >
      Private Function isValidVnaam() As Boolean
      If Me.Vnaam.Trim.L ength 0 Then
      Return True
      Else
      Return False
      End If
      End Function
      >
      Private Function isValidAnaam() As Boolean
      If Me.Anaam.Trim.L ength 0 Then
      Return True
      Else
      Return False
      End If
      End Function
      >
      Public Overloads Function CompareTo(ByVal obj As Object) As Integer
      Implements System.ICompara ble.CompareTo
      Return Me.mVnaam.Compa reTo(CType(obj, Persoon).Vnaam)
      End Function
      End Class
      *************** *************** ****
      The Form :
      *************** *************** ****
      Public Class frmBinarySearch Tree
      >
      Private Sub btnExecute_Clic k(ByVal sender As System.Object, ByVal e As
      System.EventArg s) Handles btnExecute.Clic k
      Dim bstLedenLijst As New BinarySearchTre e
      Dim bstLidnummer As New BinarySearchTre e
      Dim txtOutput As String = ""
      >
      bstLidnummer.Ad d("5")
      bstLidnummer.Ad d("2")
      bstLidnummer.Ad d("1")
      bstLidnummer.Ad d("4")
      bstLidnummer.Ad d("3")
      txtOutput = bstLidnummer.Se arch("3") & vbCrLf
      >
      bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
      bstLedenLijst.A dd(New Persoon("Jamie-Lee", "Curtis"))
      bstLedenLijst.A dd(New Persoon("Demi", "Moore"))
      bstLedenLijst.A dd(New Persoon("Julia" , "Roberts"))
      bstLedenLijst.A dd(New Persoon("Andie" , "MacDowell" ))
      >
      txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
      >
      Me.txtOutput.Te xt = txtOutput
      >
      End Sub
      >
      Private Sub btnExit_Click(B yVal sender As System.Object, ByVal e As
      System.EventArg s) Handles btnExit.Click
      Application.Exi t()
      End Sub
      >
      End Class
      >
      >
      >

        Comment

        • Jay B. Harlow
          #3
          Re: Binary Search Tree - CompareTo Error

          Doh!

          Clicked send too soon. I had the trees backwards:

          Dim bstLedenLijst As New BinarySearchTre e(Of Persoon)
          Dim bstLidnummer As New BinarySearchTre e(Of String)

          Of course this demonstrated the immediate & obvious compile time error I
          suggested ;-)

          --
          Hope this helps
          Jay B. Harlow
          ..NET Application Architect, Enthusiast, & Evangelist
          T.S. Bradley - http://www.tsbradley.net


          "BenCoo" <teddyb58@hotma il.comwrote in message
          news:CNPkh.2608 24$tk1.5394486@ phobos.telenet-ops.be...
          Hello,
          >
          In a Binary Search Tree I get the error : Object must be of type String
          >
          if I run the form only with the "Dim bstLidnummer As New
          BinarySearchTre e"
          it works fine.
          >
          Thanks for any help on this,
          >
          Benny
          >
          My BST-code lookes lokes this :
          *************** *************** *************** *****
          Class BST
          *************** *************** *************** *****
          Public Class BinarySearchTre e
          Private Class TreeNode
          Private mData As IComparable
          Private mLeftNode As TreeNode
          Private mRightNode As TreeNode
          >
          Public Sub New(ByVal data As IComparable)
          Me.mData = data
          End Sub
          >
          Public ReadOnly Property Data() As IComparable
          Get
          Return Me.mData
          End Get
          End Property
          >
          Public Property LeftNode() As TreeNode
          Get
          Return Me.mLeftNode
          End Get
          Set(ByVal value As TreeNode)
          Me.mLeftNode = value
          End Set
          End Property
          >
          Public Property RightNode() As TreeNode
          Get
          Return Me.mRightNode
          End Get
          Set(ByVal value As TreeNode)
          Me.mRightNode = value
          End Set
          End Property
          >
          Public Sub Add(ByVal data As IComparable)
          If data.CompareTo( Me.mData) <= 0 Then
          If Me.mLeftNode Is Nothing Then
          Me.mLeftNode = New TreeNode(data)
          Else
          Me.mLeftNode.Ad d(data)
          End If
          Else
          If Me.mRightNode Is Nothing Then
          Me.mRightNode = New TreeNode(data)
          Else
          Me.mRightNode.A dd(data)
          End If
          End If
          End Sub
          End Class
          >
          Private mRoot As TreeNode
          >
          Public Sub Add(ByVal data As IComparable)
          If mRoot Is Nothing Then
          mRoot = New TreeNode(data)
          Else
          mRoot.Add(data)
          End If
          End Sub
          >
          Public Function Search(ByVal data As IComparable) As Object
          Return Me.Search(data, Me.mRoot)
          End Function
          >
          Private Function Search(ByVal data As IComparable, ByVal node As
          TreeNode) As Object
          >
          If node Is Nothing Then
          Return Nothing
          Else
          Dim result As Integer = data.CompareTo( node.Data) '****** this is
          the error I get on this line :Object must be of type String.
          >
          If result = 0 Then
          Return node.Data
          ElseIf result < 0 Then
          Return Me.Search(data, node.LeftNode)
          Else
          Return Me.Search(data, node.RightNode)
          End If
          End If
          >
          End Function
          End Class
          *************** **************
          The class Person
          *************** **************
          Public Class Persoon
          Inherits BusinessObject
          Implements IComparable
          >
          Private mVnaam As String
          Private mAnaam As String
          >
          Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
          Me.mVnaam = Vnaam
          Me.mAnaam = Anaam
          End Sub
          >
          Public Property Vnaam() As String
          Get
          Return Me.mVnaam
          End Get
          Set(ByVal value As String)
          mVnaam = value
          End Set
          End Property
          >
          Public Property Anaam() As String
          Get
          Return Me.mAnaam
          End Get
          Set(ByVal value As String)
          Me.mAnaam = value
          End Set
          End Property
          >
          Public Overrides Function IsValid() As Boolean
          If Me.isValidVnaam () And Me.isValidAnaam () Then
          Return True
          Else
          Return False
          End If
          End Function
          >
          Private Function isValidVnaam() As Boolean
          If Me.Vnaam.Trim.L ength 0 Then
          Return True
          Else
          Return False
          End If
          End Function
          >
          Private Function isValidAnaam() As Boolean
          If Me.Anaam.Trim.L ength 0 Then
          Return True
          Else
          Return False
          End If
          End Function
          >
          Public Overloads Function CompareTo(ByVal obj As Object) As Integer
          Implements System.ICompara ble.CompareTo
          Return Me.mVnaam.Compa reTo(CType(obj, Persoon).Vnaam)
          End Function
          End Class
          *************** *************** ****
          The Form :
          *************** *************** ****
          Public Class frmBinarySearch Tree
          >
          Private Sub btnExecute_Clic k(ByVal sender As System.Object, ByVal e As
          System.EventArg s) Handles btnExecute.Clic k
          Dim bstLedenLijst As New BinarySearchTre e
          Dim bstLidnummer As New BinarySearchTre e
          Dim txtOutput As String = ""
          >
          bstLidnummer.Ad d("5")
          bstLidnummer.Ad d("2")
          bstLidnummer.Ad d("1")
          bstLidnummer.Ad d("4")
          bstLidnummer.Ad d("3")
          txtOutput = bstLidnummer.Se arch("3") & vbCrLf
          >
          bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
          bstLedenLijst.A dd(New Persoon("Jamie-Lee", "Curtis"))
          bstLedenLijst.A dd(New Persoon("Demi", "Moore"))
          bstLedenLijst.A dd(New Persoon("Julia" , "Roberts"))
          bstLedenLijst.A dd(New Persoon("Andie" , "MacDowell" ))
          >
          txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
          >
          Me.txtOutput.Te xt = txtOutput
          >
          End Sub
          >
          Private Sub btnExit_Click(B yVal sender As System.Object, ByVal e As
          System.EventArg s) Handles btnExit.Click
          Application.Exi t()
          End Sub
          >
          End Class
          >
          >
          >

            Comment

            • Jay B. Harlow
              #4
              Re: Binary Search Tree - CompareTo Error

              Reviewing this, one more change:

              Public Function Search(ByVal data As T) As T
              Return Me.Search(data, Me.mRoot)
              End Function

              Private Function Search(ByVal data As T, ByVal node As TreeNode) As T

              If node Is Nothing Then
              Return Nothing
              Else
              Dim result As Integer = data.CompareTo( node.Data) '****** this
              is the error I get on this line :Object must be of type String.

              If result = 0 Then
              Return node.Data
              ElseIf result < 0 Then
              Return Me.Search(data, node.LeftNode)
              Else
              Return Me.Search(data, node.RightNode)
              End If
              End If

              Note that Search returns type T; this ensures that BinarySearchTre e(Of T) is
              type safe and performant. performant in that the data will not be boxed. (in
              the case of BinarySearchTre e(Of Integer))

              Although I would recommend defining Search as:

              Public Function Search(ByVal match As Predicate(Of T)) As T

              Or even:

              Public Delegate Function Predicate(Of T, V)(ByVal obj As T, ByVal value
              As V) As Boolean

              Public Function Search(Of V)(ByVal value As V, ByVal match As
              Predicate(Of T, V)) As T

              Which I will leave as an exercise for you to complete...

              --
              Hope this helps
              Jay B. Harlow
              ..NET Application Architect, Enthusiast, & Evangelist
              T.S. Bradley - http://www.tsbradley.net


              "Jay B. Harlow" <Jay_Harlow_MVP @tsbradley.netw rote in message
              news:eIm21joKHH A.3268@TK2MSFTN GP04.phx.gbl...
              BenCoo,
              Interesting homework assignment; I miss those days...
              >
              Anyway to answer your question:
              >
              > Dim bstLedenLijst As New BinarySearchTre e
              > Dim bstLidnummer As New BinarySearchTre e
              > Dim txtOutput As String = ""
              >>
              > bstLidnummer.Ad d("5")
              > txtOutput = bstLidnummer.Se arch("3") & vbCrLf
              >>
              > bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
              >>
              > txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
              >
              Ah! There's the Rub!
              >
              bstLedenLijst contains a collection of Persoon objects, you are attempting
              to compare Persoon objects to a String object! You need to pass a Persoon
              object to bstLedenLijst.S earch. I would recommend you change
              BinarySearchTre e to a Generic class; changing this obscure runtime error
              into an obvious compile time error!
              >
              Something like:
              >
              Public Class BinarySearchTre e(Of T As IComparable)
              >
              Private Class TreeNode
              Private mData As T
              Private mLeftNode As TreeNode
              Private mRightNode As TreeNode
              >
              Public Sub New(ByVal data As T)
              Me.mData = data
              End Sub
              >
              Public ReadOnly Property Data() As T
              Get
              Return Me.mData
              End Get
              End Property
              >
              Public Property LeftNode() As TreeNode
              Get
              Return Me.mLeftNode
              End Get
              Set(ByVal value As TreeNode)
              Me.mLeftNode = value
              End Set
              End Property
              >
              Public Property RightNode() As TreeNode
              Get
              Return Me.mRightNode
              End Get
              Set(ByVal value As TreeNode)
              Me.mRightNode = value
              End Set
              End Property
              >
              Public Sub Add(ByVal data As T)
              If data.CompareTo( Me.mData) <= 0 Then
              If Me.mLeftNode Is Nothing Then
              Me.mLeftNode = New TreeNode(data)
              Else
              Me.mLeftNode.Ad d(data)
              End If
              Else
              If Me.mRightNode Is Nothing Then
              Me.mRightNode = New TreeNode(data)
              Else
              Me.mRightNode.A dd(data)
              End If
              End If
              End Sub
              End Class
              >
              Private mRoot As TreeNode
              >
              Public Sub Add(ByVal data As T)
              If mRoot Is Nothing Then
              mRoot = New TreeNode(data)
              Else
              mRoot.Add(data)
              End If
              End Sub
              >
              Public Function Search(ByVal data As T) As Object
              Return Me.Search(data, Me.mRoot)
              End Function
              >
              Private Function Search(ByVal data As T, ByVal node As TreeNode) As
              Object
              >
              If node Is Nothing Then
              Return Nothing
              Else
              Dim result As Integer = data.CompareTo( node.Data) '****** this
              is the error I get on this line :Object must be of type String.
              >
              If result = 0 Then
              Return node.Data
              ElseIf result < 0 Then
              Return Me.Search(data, node.LeftNode)
              Else
              Return Me.Search(data, node.RightNode)
              End If
              End If
              >
              End Function
              End Class
              >
              Then when you define your trees, you give the type of tree they are!
              >
              > Dim bstLedenLijst As New BinarySearchTre e(Of String)
              > Dim bstLidnummer As New BinarySearchTre e(Of Persoon)
              >
              NOTE: You need VS 2005 for generics.
              >
              --
              Hope this helps
              Jay B. Harlow
              .NET Application Architect, Enthusiast, & Evangelist
              T.S. Bradley - http://www.tsbradley.net
              >
              >
              "BenCoo" <teddyb58@hotma il.comwrote in message
              news:CNPkh.2608 24$tk1.5394486@ phobos.telenet-ops.be...
              >Hello,
              >>
              >In a Binary Search Tree I get the error : Object must be of type String
              >>
              >if I run the form only with the "Dim bstLidnummer As New
              >BinarySearchTr ee"
              >it works fine.
              >>
              >Thanks for any help on this,
              >>
              >Benny
              >>
              >My BST-code lookes lokes this :
              >************** *************** *************** ******
              >Class BST
              >************** *************** *************** ******
              >Public Class BinarySearchTre e
              > Private Class TreeNode
              > Private mData As IComparable
              > Private mLeftNode As TreeNode
              > Private mRightNode As TreeNode
              >>
              > Public Sub New(ByVal data As IComparable)
              > Me.mData = data
              > End Sub
              >>
              > Public ReadOnly Property Data() As IComparable
              > Get
              > Return Me.mData
              > End Get
              > End Property
              >>
              > Public Property LeftNode() As TreeNode
              > Get
              > Return Me.mLeftNode
              > End Get
              > Set(ByVal value As TreeNode)
              > Me.mLeftNode = value
              > End Set
              > End Property
              >>
              > Public Property RightNode() As TreeNode
              > Get
              > Return Me.mRightNode
              > End Get
              > Set(ByVal value As TreeNode)
              > Me.mRightNode = value
              > End Set
              > End Property
              >>
              > Public Sub Add(ByVal data As IComparable)
              > If data.CompareTo( Me.mData) <= 0 Then
              > If Me.mLeftNode Is Nothing Then
              > Me.mLeftNode = New TreeNode(data)
              > Else
              > Me.mLeftNode.Ad d(data)
              > End If
              > Else
              > If Me.mRightNode Is Nothing Then
              > Me.mRightNode = New TreeNode(data)
              > Else
              > Me.mRightNode.A dd(data)
              > End If
              > End If
              > End Sub
              > End Class
              >>
              > Private mRoot As TreeNode
              >>
              > Public Sub Add(ByVal data As IComparable)
              > If mRoot Is Nothing Then
              > mRoot = New TreeNode(data)
              > Else
              > mRoot.Add(data)
              > End If
              > End Sub
              >>
              > Public Function Search(ByVal data As IComparable) As Object
              > Return Me.Search(data, Me.mRoot)
              > End Function
              >>
              > Private Function Search(ByVal data As IComparable, ByVal node As
              >TreeNode) As Object
              >>
              > If node Is Nothing Then
              > Return Nothing
              > Else
              > Dim result As Integer = data.CompareTo( node.Data) '****** this
              >is
              >the error I get on this line :Object must be of type String.
              >>
              > If result = 0 Then
              > Return node.Data
              > ElseIf result < 0 Then
              > Return Me.Search(data, node.LeftNode)
              > Else
              > Return Me.Search(data, node.RightNode)
              > End If
              > End If
              >>
              > End Function
              >End Class
              >************** ***************
              >The class Person
              >************** ***************
              >Public Class Persoon
              > Inherits BusinessObject
              > Implements IComparable
              >>
              > Private mVnaam As String
              > Private mAnaam As String
              >>
              > Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
              > Me.mVnaam = Vnaam
              > Me.mAnaam = Anaam
              > End Sub
              >>
              > Public Property Vnaam() As String
              > Get
              > Return Me.mVnaam
              > End Get
              > Set(ByVal value As String)
              > mVnaam = value
              > End Set
              > End Property
              >>
              > Public Property Anaam() As String
              > Get
              > Return Me.mAnaam
              > End Get
              > Set(ByVal value As String)
              > Me.mAnaam = value
              > End Set
              > End Property
              >>
              > Public Overrides Function IsValid() As Boolean
              > If Me.isValidVnaam () And Me.isValidAnaam () Then
              > Return True
              > Else
              > Return False
              > End If
              > End Function
              >>
              > Private Function isValidVnaam() As Boolean
              > If Me.Vnaam.Trim.L ength 0 Then
              > Return True
              > Else
              > Return False
              > End If
              > End Function
              >>
              > Private Function isValidAnaam() As Boolean
              > If Me.Anaam.Trim.L ength 0 Then
              > Return True
              > Else
              > Return False
              > End If
              > End Function
              >>
              > Public Overloads Function CompareTo(ByVal obj As Object) As Integer
              >Implements System.ICompara ble.CompareTo
              > Return Me.mVnaam.Compa reTo(CType(obj, Persoon).Vnaam)
              > End Function
              >End Class
              >************** *************** *****
              >The Form :
              >************** *************** *****
              >Public Class frmBinarySearch Tree
              >>
              > Private Sub btnExecute_Clic k(ByVal sender As System.Object, ByVal e As
              >System.EventAr gs) Handles btnExecute.Clic k
              > Dim bstLedenLijst As New BinarySearchTre e
              > Dim bstLidnummer As New BinarySearchTre e
              > Dim txtOutput As String = ""
              >>
              > bstLidnummer.Ad d("5")
              > bstLidnummer.Ad d("2")
              > bstLidnummer.Ad d("1")
              > bstLidnummer.Ad d("4")
              > bstLidnummer.Ad d("3")
              > txtOutput = bstLidnummer.Se arch("3") & vbCrLf
              >>
              > bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
              > bstLedenLijst.A dd(New Persoon("Jamie-Lee", "Curtis"))
              > bstLedenLijst.A dd(New Persoon("Demi", "Moore"))
              > bstLedenLijst.A dd(New Persoon("Julia" , "Roberts"))
              > bstLedenLijst.A dd(New Persoon("Andie" , "MacDowell" ))
              >>
              > txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
              >>
              > Me.txtOutput.Te xt = txtOutput
              >>
              > End Sub
              >>
              > Private Sub btnExit_Click(B yVal sender As System.Object, ByVal e As
              >System.EventAr gs) Handles btnExit.Click
              > Application.Exi t()
              > End Sub
              >>
              >End Class
              >>
              >>
              >>
              >

                Comment

                • BenCoo
                  #5
                  Re: Binary Search Tree - CompareTo Error

                  Thank you for your quick response; I solved afther the poste was made the
                  promlem this way ..

                  Dim zoekPersoon As New Persoon(Me.txtZ oek.Text, "")

                  Console.WriteLi ne(bstLedenLijs t.Search(zoekPe rsoon))





                  "Jay B. Harlow" <Jay_Harlow_MVP @tsbradley.nets chreef in bericht
                  news:eIm21joKHH A.3268@TK2MSFTN GP04.phx.gbl...
                  BenCoo,
                  Interesting homework assignment; I miss those days...
                  >
                  Anyway to answer your question:
                  >
                  > Dim bstLedenLijst As New BinarySearchTre e
                  > Dim bstLidnummer As New BinarySearchTre e
                  > Dim txtOutput As String = ""
                  >>
                  > bstLidnummer.Ad d("5")
                  > txtOutput = bstLidnummer.Se arch("3") & vbCrLf
                  >>
                  > bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
                  >>
                  > txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
                  >
                  Ah! There's the Rub!
                  >
                  bstLedenLijst contains a collection of Persoon objects, you are attempting
                  to compare Persoon objects to a String object! You need to pass a Persoon
                  object to bstLedenLijst.S earch. I would recommend you change
                  BinarySearchTre e to a Generic class; changing this obscure runtime error
                  into an obvious compile time error!
                  >
                  Something like:
                  >
                  Public Class BinarySearchTre e(Of T As IComparable)
                  >
                  Private Class TreeNode
                  Private mData As T
                  Private mLeftNode As TreeNode
                  Private mRightNode As TreeNode
                  >
                  Public Sub New(ByVal data As T)
                  Me.mData = data
                  End Sub
                  >
                  Public ReadOnly Property Data() As T
                  Get
                  Return Me.mData
                  End Get
                  End Property
                  >
                  Public Property LeftNode() As TreeNode
                  Get
                  Return Me.mLeftNode
                  End Get
                  Set(ByVal value As TreeNode)
                  Me.mLeftNode = value
                  End Set
                  End Property
                  >
                  Public Property RightNode() As TreeNode
                  Get
                  Return Me.mRightNode
                  End Get
                  Set(ByVal value As TreeNode)
                  Me.mRightNode = value
                  End Set
                  End Property
                  >
                  Public Sub Add(ByVal data As T)
                  If data.CompareTo( Me.mData) <= 0 Then
                  If Me.mLeftNode Is Nothing Then
                  Me.mLeftNode = New TreeNode(data)
                  Else
                  Me.mLeftNode.Ad d(data)
                  End If
                  Else
                  If Me.mRightNode Is Nothing Then
                  Me.mRightNode = New TreeNode(data)
                  Else
                  Me.mRightNode.A dd(data)
                  End If
                  End If
                  End Sub
                  End Class
                  >
                  Private mRoot As TreeNode
                  >
                  Public Sub Add(ByVal data As T)
                  If mRoot Is Nothing Then
                  mRoot = New TreeNode(data)
                  Else
                  mRoot.Add(data)
                  End If
                  End Sub
                  >
                  Public Function Search(ByVal data As T) As Object
                  Return Me.Search(data, Me.mRoot)
                  End Function
                  >
                  Private Function Search(ByVal data As T, ByVal node As TreeNode) As
                  Object
                  >
                  If node Is Nothing Then
                  Return Nothing
                  Else
                  Dim result As Integer = data.CompareTo( node.Data) '****** this
                  is the error I get on this line :Object must be of type String.
                  >
                  If result = 0 Then
                  Return node.Data
                  ElseIf result < 0 Then
                  Return Me.Search(data, node.LeftNode)
                  Else
                  Return Me.Search(data, node.RightNode)
                  End If
                  End If
                  >
                  End Function
                  End Class
                  >
                  Then when you define your trees, you give the type of tree they are!
                  >
                  > Dim bstLedenLijst As New BinarySearchTre e(Of String)
                  > Dim bstLidnummer As New BinarySearchTre e(Of Persoon)
                  >
                  NOTE: You need VS 2005 for generics.
                  >
                  --
                  Hope this helps
                  Jay B. Harlow
                  .NET Application Architect, Enthusiast, & Evangelist
                  T.S. Bradley - http://www.tsbradley.net
                  >
                  >
                  "BenCoo" <teddyb58@hotma il.comwrote in message
                  news:CNPkh.2608 24$tk1.5394486@ phobos.telenet-ops.be...
                  >Hello,
                  >>
                  >In a Binary Search Tree I get the error : Object must be of type String
                  >>
                  >if I run the form only with the "Dim bstLidnummer As New
                  >BinarySearchTr ee"
                  >it works fine.
                  >>
                  >Thanks for any help on this,
                  >>
                  >Benny
                  >>
                  >My BST-code lookes lokes this :
                  >************** *************** *************** ******
                  >Class BST
                  >************** *************** *************** ******
                  >Public Class BinarySearchTre e
                  > Private Class TreeNode
                  > Private mData As IComparable
                  > Private mLeftNode As TreeNode
                  > Private mRightNode As TreeNode
                  >>
                  > Public Sub New(ByVal data As IComparable)
                  > Me.mData = data
                  > End Sub
                  >>
                  > Public ReadOnly Property Data() As IComparable
                  > Get
                  > Return Me.mData
                  > End Get
                  > End Property
                  >>
                  > Public Property LeftNode() As TreeNode
                  > Get
                  > Return Me.mLeftNode
                  > End Get
                  > Set(ByVal value As TreeNode)
                  > Me.mLeftNode = value
                  > End Set
                  > End Property
                  >>
                  > Public Property RightNode() As TreeNode
                  > Get
                  > Return Me.mRightNode
                  > End Get
                  > Set(ByVal value As TreeNode)
                  > Me.mRightNode = value
                  > End Set
                  > End Property
                  >>
                  > Public Sub Add(ByVal data As IComparable)
                  > If data.CompareTo( Me.mData) <= 0 Then
                  > If Me.mLeftNode Is Nothing Then
                  > Me.mLeftNode = New TreeNode(data)
                  > Else
                  > Me.mLeftNode.Ad d(data)
                  > End If
                  > Else
                  > If Me.mRightNode Is Nothing Then
                  > Me.mRightNode = New TreeNode(data)
                  > Else
                  > Me.mRightNode.A dd(data)
                  > End If
                  > End If
                  > End Sub
                  > End Class
                  >>
                  > Private mRoot As TreeNode
                  >>
                  > Public Sub Add(ByVal data As IComparable)
                  > If mRoot Is Nothing Then
                  > mRoot = New TreeNode(data)
                  > Else
                  > mRoot.Add(data)
                  > End If
                  > End Sub
                  >>
                  > Public Function Search(ByVal data As IComparable) As Object
                  > Return Me.Search(data, Me.mRoot)
                  > End Function
                  >>
                  > Private Function Search(ByVal data As IComparable, ByVal node As
                  >TreeNode) As Object
                  >>
                  > If node Is Nothing Then
                  > Return Nothing
                  > Else
                  > Dim result As Integer = data.CompareTo( node.Data) '****** this
                  >is
                  >the error I get on this line :Object must be of type String.
                  >>
                  > If result = 0 Then
                  > Return node.Data
                  > ElseIf result < 0 Then
                  > Return Me.Search(data, node.LeftNode)
                  > Else
                  > Return Me.Search(data, node.RightNode)
                  > End If
                  > End If
                  >>
                  > End Function
                  >End Class
                  >************** ***************
                  >The class Person
                  >************** ***************
                  >Public Class Persoon
                  > Inherits BusinessObject
                  > Implements IComparable
                  >>
                  > Private mVnaam As String
                  > Private mAnaam As String
                  >>
                  > Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
                  > Me.mVnaam = Vnaam
                  > Me.mAnaam = Anaam
                  > End Sub
                  >>
                  > Public Property Vnaam() As String
                  > Get
                  > Return Me.mVnaam
                  > End Get
                  > Set(ByVal value As String)
                  > mVnaam = value
                  > End Set
                  > End Property
                  >>
                  > Public Property Anaam() As String
                  > Get
                  > Return Me.mAnaam
                  > End Get
                  > Set(ByVal value As String)
                  > Me.mAnaam = value
                  > End Set
                  > End Property
                  >>
                  > Public Overrides Function IsValid() As Boolean
                  > If Me.isValidVnaam () And Me.isValidAnaam () Then
                  > Return True
                  > Else
                  > Return False
                  > End If
                  > End Function
                  >>
                  > Private Function isValidVnaam() As Boolean
                  > If Me.Vnaam.Trim.L ength 0 Then
                  > Return True
                  > Else
                  > Return False
                  > End If
                  > End Function
                  >>
                  > Private Function isValidAnaam() As Boolean
                  > If Me.Anaam.Trim.L ength 0 Then
                  > Return True
                  > Else
                  > Return False
                  > End If
                  > End Function
                  >>
                  > Public Overloads Function CompareTo(ByVal obj As Object) As Integer
                  >Implements System.ICompara ble.CompareTo
                  > Return Me.mVnaam.Compa reTo(CType(obj, Persoon).Vnaam)
                  > End Function
                  >End Class
                  >************** *************** *****
                  >The Form :
                  >************** *************** *****
                  >Public Class frmBinarySearch Tree
                  >>
                  > Private Sub btnExecute_Clic k(ByVal sender As System.Object, ByVal e As
                  >System.EventAr gs) Handles btnExecute.Clic k
                  > Dim bstLedenLijst As New BinarySearchTre e
                  > Dim bstLidnummer As New BinarySearchTre e
                  > Dim txtOutput As String = ""
                  >>
                  > bstLidnummer.Ad d("5")
                  > bstLidnummer.Ad d("2")
                  > bstLidnummer.Ad d("1")
                  > bstLidnummer.Ad d("4")
                  > bstLidnummer.Ad d("3")
                  > txtOutput = bstLidnummer.Se arch("3") & vbCrLf
                  >>
                  > bstLedenLijst.A dd(New Persoon("Nicole ", "Kidman"))
                  > bstLedenLijst.A dd(New Persoon("Jamie-Lee", "Curtis"))
                  > bstLedenLijst.A dd(New Persoon("Demi", "Moore"))
                  > bstLedenLijst.A dd(New Persoon("Julia" , "Roberts"))
                  > bstLedenLijst.A dd(New Persoon("Andie" , "MacDowell" ))
                  >>
                  > txtOutput &= bstLedenLijst.S earch("Demi") ' & vbCrLf
                  >>
                  > Me.txtOutput.Te xt = txtOutput
                  >>
                  > End Sub
                  >>
                  > Private Sub btnExit_Click(B yVal sender As System.Object, ByVal e As
                  >System.EventAr gs) Handles btnExit.Click
                  > Application.Exi t()
                  > End Sub
                  >>
                  >End Class
                  >>
                  >>
                  >>
                  >

                    Comment

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