• Call the DataAdapter.FillSchema method to obtain extended schema information.
• Set DataAdapter.MissingSchemaAction to MissingSchemaAction.AddWithKey before you call the Fill method.

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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.
4. Place a Button control and a DataGrid control on Form1.
5. Change the Name property of the button to btnTest and the Text property to Test.
6. Use the Imports statement on the System and System.Data namespaces so that you are not required to qualify declarations in those namespaces later in your code. Add the following code to the "General Declarations" section of Form1:

   Imports System
   Imports System.Data.OleDb
   Imports System.Data.SqlClient
   					

7. Add 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 myConnString As String = _
                   "User ID=sa;password=sa;Initial Catalog=Northwind;Data Source=myServer"
           Dim ds As New DataSet()
           Dim con As New SqlConnection(myConnString)
           Dim daCust As New SqlDataAdapter("Select * From Customers", con)
           'Uncomment either of the following two lines to obtain additional schema information.
           'daCust.MissingSchemaAction = MissingSchemaAction.AddWithKey
           'daCust.FillSchema(ds, SchemaType.Source, "Cust")
           daCust.Fill(ds, "Cust")
   
           DataGrid1.DataSource = ds
           DataGrid1.DataMember = "Cust"
   
           Dim colArr() As DataColumn
           colArr = ds.Tables(0).PrimaryKey
           If colArr.Length.ToString() = 0 Then
               MessageBox.Show("No Primary Key is defined.")
           End If
   
           Dim i As Integer
           For i = 0 To colArr.GetUpperBound(0)
               MessageBox.Show("Primary Key : " & colArr(i).ColumnName)
           Next i
       End Sub
   					

8. Modify the connection string (myConnString) as appropriate for your environment.
9. Save your project. On the Debug menu, click Start to run your project.
10. Click Test. Notice that you cannot retrieve the primary key information from the table.
11. Uncomment the code to either set MissingSchemaAction or use FillSchema, and then click Test again. Notice that the primary key information is retrieved properly.

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