ASP.net merge two datasets

Hi

What is the easiest way to merge two datasets that have the same first two columns, and that are created using code like the following


    Function GetData(ByVal queryString As String) As DataSet

        Dim cs As String = ConfigurationManager.ConnectionStrings("survey_conn").ConnectionString
        Dim myConnection As SqlConnection = New SqlConnection(cs)

        Dim ds As New DataSet()

        Try

            ' Connect to the database and run the query.

            Dim adapter As New SqlDataAdapter(queryString, myConnection)
            ' Fill the DataSet.
            Adapter.Fill(ds)


        Catch ex As Exception

            ' The connection failed. Display an error message.
            Me.Label_Error1.Text = "Unable to connect to the database." & Err.Description

        End Try

        Return ds

    End Function