Steps to Reproduce the Behavior

1. Start Microsoft Visual Studio .NET.
2. Create a new Windows Application project in Visual Basic .NET. Form1 is added to the project by default.
3. Make sure that your project contains a reference to the System.Data namespace, and add a reference to this namespace if it does not.
4. Place a Button control on Form1, and change its Name property to btnTest.
5. Use the Imports statement on the System, System.Data, System.Data.Common, and System.Data.OleDb namespaces so that you are not required to qualify declarations in those namespaces later in your code.

   Imports System
   Imports System.Data
   Imports System.Data.Common
   Imports System.Data.OleDb
   					

6. Paste the following code in the Code window after the "Windows Form Designer generated code" region:

       Private Sub btnTest_Click(ByVal sender As System.Object, _
       ByVal e As System.EventArgs) Handles btnTest.Click
           Dim myDataAdapter As New OleDbDataAdapter()
           myDataAdapter.TableMappings.Add("Categories", "DataCategories")
   
           Dim myMessage As String = "Table Mappings:" + ControlChars.Cr
           Dim i As Integer
           For i = 0 To myDataAdapter.TableMappings.Count - 1
               myMessage += i.ToString() + " " _
                  + myDataAdapter.TableMappings(i).ToString() + ControlChars.Cr
           Next i
           MessageBox.Show(myMessage)
   
           Dim myNewMapping As New DataTableMapping()
   
           'Uncomment the if loop to check if the column mapping that you specify exists.
           'If myDataAdapter.TableMappings.Contains("Categories1") Then
               myNewMapping = DataTableMappingCollection.GetTableMappingBySchemaAction _
                  (myDataAdapter.TableMappings, "Categories1", "", MissingMappingAction.Error)
           'End If
       End Sub
   					

7. Save your project. On the Debug menu, click Start, and then run your project.
8. Click the button. You receive the above-mentioned exception.
9. To resolve this problem, uncomment the "if" loop in the preceding sample code, and then run the project again. Because the "if" loop checks whether the specified column mapping exists, you no longer receive the exception.

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