VB.Net - checking for Null values in DataSets

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  • Martyn Fewtrell
    #1

    VB.Net - checking for Null values in DataSets

    Hi there.

    I wonder if there was a "correct answer" for Vb.Net (I understand this is
    quite easy in C#).

    If im drawing data from a database using a TableAdapter the data ends up in
    a DataTable. I then need to iterate through the DataTable to get the values
    out. This in itself is not a big issue.

    Code something like...

    For x = 0 to........

    myString = DataTable.Rows( x).Item("MyValu e")

    until I come across a Null value.

    A Null value in the Database throws an exception which is easy to address
    with a Try Catch statement. However as mentioned in some of the excellent
    articles this is not a good solution for the problem.

    Is there some means of testing the value before accessing it so that the
    Try/Catch would no longer be required.

    Perhaps something like:

    If Not Datatable.Rows( 0).Item("MyValu e") = Nothing Then

    myString = DataTable.Rows( 0).Item("MyValu e")

    End If

    Which doesnt work!

    Try/Catch just seems the wrong approach.


    Regards

    Martyn Fewtrell
    Tags: None
    • Patrick.O.Ige
      #2
      Re: VB.Net - checking for Null values in DataSets

      Martyn trying checking fo DBNull.value
      Hope that helps
      Patrick

      "Martyn Fewtrell" <mfewtrell@news group.nospamwro te in message
      news:88DDAC44-6924-4C1A-AC78-DE07051E7526@mi crosoft.com...
      Hi there.
      >
      I wonder if there was a "correct answer" for Vb.Net (I understand this is
      quite easy in C#).
      >
      If im drawing data from a database using a TableAdapter the data ends up
      in
      a DataTable. I then need to iterate through the DataTable to get the
      values
      out. This in itself is not a big issue.
      >
      Code something like...
      >
      For x = 0 to........
      >
      myString = DataTable.Rows( x).Item("MyValu e")
      >
      until I come across a Null value.
      >
      A Null value in the Database throws an exception which is easy to address
      with a Try Catch statement. However as mentioned in some of the excellent
      articles this is not a good solution for the problem.
      >
      Is there some means of testing the value before accessing it so that the
      Try/Catch would no longer be required.
      >
      Perhaps something like:
      >
      If Not Datatable.Rows( 0).Item("MyValu e") = Nothing Then
      >
      myString = DataTable.Rows( 0).Item("MyValu e")
      >
      End If
      >
      Which doesnt work!
      >
      Try/Catch just seems the wrong approach.
      >
      >
      Regards
      >
      Martyn Fewtrell

        Comment

        • Cowboy \(Gregory A. Beamer\)
          #3
          Re: VB.Net - checking for Null values in DataSets

          Compare to DBNull.Value.

          --
          Gregory A. Beamer
          MVP; MCP: +I, SE, SD, DBA

          *************** *************** *************** ****
          Think outside of the box!
          *************** *************** *************** ****
          "Martyn Fewtrell" <mfewtrell@news group.nospamwro te in message
          news:88DDAC44-6924-4C1A-AC78-DE07051E7526@mi crosoft.com...
          Hi there.
          >
          I wonder if there was a "correct answer" for Vb.Net (I understand this is
          quite easy in C#).
          >
          If im drawing data from a database using a TableAdapter the data ends up
          in
          a DataTable. I then need to iterate through the DataTable to get the
          values
          out. This in itself is not a big issue.
          >
          Code something like...
          >
          For x = 0 to........
          >
          myString = DataTable.Rows( x).Item("MyValu e")
          >
          until I come across a Null value.
          >
          A Null value in the Database throws an exception which is easy to address
          with a Try Catch statement. However as mentioned in some of the excellent
          articles this is not a good solution for the problem.
          >
          Is there some means of testing the value before accessing it so that the
          Try/Catch would no longer be required.
          >
          Perhaps something like:
          >
          If Not Datatable.Rows( 0).Item("MyValu e") = Nothing Then
          >
          myString = DataTable.Rows( 0).Item("MyValu e")
          >
          End If
          >
          Which doesnt work!
          >
          Try/Catch just seems the wrong approach.
          >
          >
          Regards
          >
          Martyn Fewtrell

            Comment

            • Martyn Fewtrell
              #4
              Re: VB.Net - checking for Null values in DataSets

              Thanks to both of you.

              I've gone with

              If Not (IsDBNull(DataT able.Rows(x).It em("MyValue")) ) Then
              myString = DataTable.Rows( x).Item("MyValu e")
              End If

              Which seems to do the trick!

              --
              Regards

              Martyn Fewtrell


              "Cowboy (Gregory A. Beamer)" wrote:
              Compare to DBNull.Value.
              >
              --
              Gregory A. Beamer
              MVP; MCP: +I, SE, SD, DBA
              >
              *************** *************** *************** ****
              Think outside of the box!
              *************** *************** *************** ****
              "Martyn Fewtrell" <mfewtrell@news group.nospamwro te in message
              news:88DDAC44-6924-4C1A-AC78-DE07051E7526@mi crosoft.com...
              Hi there.

              I wonder if there was a "correct answer" for Vb.Net (I understand this is
              quite easy in C#).

              If im drawing data from a database using a TableAdapter the data ends up
              in
              a DataTable. I then need to iterate through the DataTable to get the
              values
              out. This in itself is not a big issue.

              Code something like...

              For x = 0 to........

              myString = DataTable.Rows( x).Item("MyValu e")

              until I come across a Null value.

              A Null value in the Database throws an exception which is easy to address
              with a Try Catch statement. However as mentioned in some of the excellent
              articles this is not a good solution for the problem.

              Is there some means of testing the value before accessing it so that the
              Try/Catch would no longer be required.

              Perhaps something like:

              If Not Datatable.Rows( 0).Item("MyValu e") = Nothing Then

              myString = DataTable.Rows( 0).Item("MyValu e")

              End If

              Which doesnt work!

              Try/Catch just seems the wrong approach.


              Regards

              Martyn Fewtrell
              >
              >
              >

                Comment

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