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ASP.Net error. Cannot cast object of type "System.String" to type "System.Data.DataTable"

I am getting the following error

Cannot cast object of type 'System.String' to type 'System.Data.DataTable'.

This is the code I am using

Dim str As String = String.Empty

    If (Session("Brief") IsNot Nothing) Then

        Dim dt As DataTable = Session("Brief")
        If (dt.Rows.Count > 0) Then
            For Each dr As DataRow In dt.Rows
                If (str.Length > 0) Then str += ","
                str += dr("talentID").ToString()
            Next
        End If

    End If

    Return str

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3 answers


I'm not a VB guy, but I would have thought that you would need to cast your session variable to the correct type (DataTable):



Dim dt As DataTable = CType(Session("Brief"), DataTable);
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I think you need to "merge" the session ("Brief"):

Dim dt As DataTable = CType(Session("Brief"), Datatable)


see example here

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How about this:

Dim str As String = ""

If Not Session("Brief") Is Nothing Then
  Dim dt As DataTable = TryCast(Session("Brief"), DataTable)

  If Not dt Is Nothing AndAlso dt.Rows.Count > 0 Then
    For Each dr As DataRow In dt.Rows
      If (str.Length > 0) Then
        str += ","
      End If

      str += dr("talentID").ToString()
    Next
  End If
End If

Return str

Use TryCast and the execution check was successful or not ...

And here's a version with a bit of LINQ thrown in for good measure:

Dim str As String = ""

If Not Session("Brief") Is Nothing Then
  Dim dt As DataTable = TryCast(Session("Brief"), DataTable)

  If Not dt Is Nothing AndAlso dt.Rows.Count > 0 Then
    str = Join((From r In dt Select CStr(r("talentID"))).ToArray, ",")
  End If
End If

Return str
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