Find in Collection

**Herfried K. Wagner [MVP]** · Dec 1 '05, 03:57 PM

Re: Find in Collection

Joerg,

"Joerg Battermann" <jb@justbe.co m> schrieb:[color=blue]
> I have a custom type defined via
>
> [...]
> Public Class Requirement
> Public IDNumber As Integer
> Public Name As String
> Public Description As String
> Public VersionPlanAttr ibutes As New _
> System.Collecti ons.Generic.Lis t(Of Attribute)
> Public Traces As New System.Collecti ons.Generic.Lis t(Of Trace)
> Public Checked As Boolean = False
> End Class
> [...]
>
> and want to find one particular item (identified via IDNumber) in a filled
> collection of these items declared via
>
> [...]
> Public ERSRequirements As New System.Collecti ons.Generic.Lis t(Of_
> Requirement)
> [...]
>
>
> .. is there any quick way to do it or would I have to loop through the
> collection?[/color]

\\\
Public Class Form1
Private Sub Test()
Dim x As New List(Of Person)
x.Add(New Person("Peter", 1099))
x.Add(New Person("Frank", 342234))
x.Add(New Person("Fergus" , 23423))
x.Add(New Person("Bill", 234))
Dim p As Person = _
x.Find(New Predicate(Of Person)(Address Of GetFrank))
MsgBox(p.Name)
End Sub

Private Function GetFrank( _
ByVal obj As Person _
) As Boolean
Return obj.Name = "Frank"
End Function
End Class

Public Class Person
Public Sub New(ByVal Name As String, ByVal Salary As Double)
Me.Name = Name
Me.Salary = Salary
End Sub

Public Name As String
Public Salary As Double
End Class
///

Collections are unsorted, thus runtime is in O(n) if the collection contains
n items.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

**Joerg Battermann** · Dec 1 '05, 03:57 PM

Re: Find in Collection

Hey there,

thanks for the quick reply, however is it possible to define a name in
your example using the Predicate(Of Person)(Address Of GetFrank)?

I am calling a function with an IDNumber as variable and it shall find
me the one Requirement that has that particular IDNumber... and return
it or do something with it

does this make sense?

-j

Herfried K. Wagner [MVP] wrote:[color=blue]
> Joerg,
>
> "Joerg Battermann" <jb@justbe.co m> schrieb:[color=green]
>> I have a custom type defined via
>>
>> [...]
>> Public Class Requirement
>> Public IDNumber As Integer
>> Public Name As String
>> Public Description As String
>> Public VersionPlanAttr ibutes As New _
>> System.Collecti ons.Generic.Lis t(Of Attribute)
>> Public Traces As New System.Collecti ons.Generic.Lis t(Of Trace)
>> Public Checked As Boolean = False
>> End Class
>> [...]
>>
>> and want to find one particular item (identified via IDNumber) in a
>> filled collection of these items declared via
>>
>> [...]
>> Public ERSRequirements As New System.Collecti ons.Generic.Lis t(Of_
>> Requirement)
>> [...]
>>
>>
>> .. is there any quick way to do it or would I have to loop through the
>> collection?[/color]
>
> \\\
> Public Class Form1
> Private Sub Test()
> Dim x As New List(Of Person)
> x.Add(New Person("Peter", 1099))
> x.Add(New Person("Frank", 342234))
> x.Add(New Person("Fergus" , 23423))
> x.Add(New Person("Bill", 234))
> Dim p As Person = _
> x.Find(New Predicate(Of Person)(Address Of GetFrank))
> MsgBox(p.Name)
> End Sub
>
> Private Function GetFrank( _
> ByVal obj As Person _
> ) As Boolean
> Return obj.Name = "Frank"
> End Function
> End Class
>
> Public Class Person
> Public Sub New(ByVal Name As String, ByVal Salary As Double)
> Me.Name = Name
> Me.Salary = Salary
> End Sub
>
> Public Name As String
> Public Salary As Double
> End Class
> ///
>
> Collections are unsorted, thus runtime is in O(n) if the collection
> contains n items.
>[/color]

**Herfried K. Wagner [MVP]** · Dec 1 '05, 04:15 PM

Re: Find in Collection

"Joerg Battermann" <jb@justbe.co m> schrieb:[color=blue]
> thanks for the quick reply, however is it possible to define a name in
> your example using the Predicate(Of Person)(Address Of GetFrank)?
>
> I am calling a function with an IDNumber as variable and it shall find me
> the one Requirement that has that particular IDNumber... and return it or
> do something with it[/color]

I didn't have enough time to play around with this, but maybe the solution
below will help you solve the problem (quick and dirty!):

\\\
Public Class Form1
Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
System.EventArg s) Handles MyBase.Load
Dim x As New List(Of Person)
x.Add(New Person("Peter", 1099))
x.Add(New Person("Frank", 342234))
x.Add(New Person("Fergus" , 23423))
x.Add(New Person("Bill", 234))
Dim p As Person = (New PersonFinder()) .Find(x, "Frank")
MsgBox(p.Name)
End Sub
End Class

Public Class PersonFinder
Inherits Finder(Of Person)

Protected Overrides Function InternalFind(By Val obj As Person) As
Boolean
Return obj.Name = DirectCast(Para meters(0), String)
End Function
End Class

Public Class Person
Public Sub New(ByVal Name As String, ByVal Salary As Double)
Me.Name = Name
Me.Salary = Salary
End Sub

Public Name As String
Public Salary As Double
End Class

Public MustInherit Class Finder(Of T)
Private m_Parameters() As Object

Protected Property Parameters() As Object()
Get
Return m_Parameters
End Get
Private Set(ByVal Value As Object())
m_Parameters = Value
End Set
End Property

Public Function Find( _
ByVal List As List(Of T), _
ByVal ParamArray Parameters() As Object _
) As T
Me.Parameters = Parameters
Return List.Find(Addre ssOf InternalFind)
End Function

Protected Overridable Function InternalFind( _
ByVal obj As T _
) As Boolean
'
End Function
End Class
///

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

**Joerg Battermann** · Dec 1 '05, 05:35 PM

Re: Find in Collection

Thanks a lot!!

Herfried K. Wagner [MVP] wrote:[color=blue]
> "Joerg Battermann" <jb@justbe.co m> schrieb:[color=green]
>> thanks for the quick reply, however is it possible to define a name in
>> your example using the Predicate(Of Person)(Address Of GetFrank)?
>>
>> I am calling a function with an IDNumber as variable and it shall find
>> me the one Requirement that has that particular IDNumber... and return
>> it or do something with it[/color]
>
> I didn't have enough time to play around with this, but maybe the
> solution below will help you solve the problem (quick and dirty!):
>
> \\\
> Public Class Form1
> Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
> System.EventArg s) Handles MyBase.Load
> Dim x As New List(Of Person)
> x.Add(New Person("Peter", 1099))
> x.Add(New Person("Frank", 342234))
> x.Add(New Person("Fergus" , 23423))
> x.Add(New Person("Bill", 234))
> Dim p As Person = (New PersonFinder()) .Find(x, "Frank")
> MsgBox(p.Name)
> End Sub
> End Class
>
> Public Class PersonFinder
> Inherits Finder(Of Person)
>
> Protected Overrides Function InternalFind(By Val obj As Person) As
> Boolean
> Return obj.Name = DirectCast(Para meters(0), String)
> End Function
> End Class
>
> Public Class Person
> Public Sub New(ByVal Name As String, ByVal Salary As Double)
> Me.Name = Name
> Me.Salary = Salary
> End Sub
>
> Public Name As String
> Public Salary As Double
> End Class
>
> Public MustInherit Class Finder(Of T)
> Private m_Parameters() As Object
>
> Protected Property Parameters() As Object()
> Get
> Return m_Parameters
> End Get
> Private Set(ByVal Value As Object())
> m_Parameters = Value
> End Set
> End Property
>
> Public Function Find( _
> ByVal List As List(Of T), _
> ByVal ParamArray Parameters() As Object _
> ) As T
> Me.Parameters = Parameters
> Return List.Find(Addre ssOf InternalFind)
> End Function
>
> Protected Overridable Function InternalFind( _
> ByVal obj As T _
> ) As Boolean
> '
> End Function
> End Class
> ///
>[/color]

**Jay B. Harlow [MVP - Outlook]** · Dec 2 '05, 03:45 PM

Re: Find in Collection

Joerg,
In addition to the other comments.

I posted a sample Generic Find routine in April that uses Predicate(Of T, V)
instead of Predicate(Of T). Predicate(Of T, V) allows you to pass the value
you are looking for in addition to the object you are looking at.

See these posts:

http://groups.google.com/group/microsoft.public.dotnet.languages.vb/msg/98f83b1dab29e1c8?hl=en&

http://groups.google.com/group/microsoft.public.dotnet.languages.vb/msg/649720602d7da920?hl=en&

Reviewing the entire thread might be helpful:

http://groups.google.com/group/microsoft.public.dotnet.languages.vb/browse_frm/thread/c04cb1fc8fdc7cfd/88a682c0252de224?tvc=1&hl=en#88a682c0252de224

Find in Collection

Find in Collection

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