Private Shared Sub DemonstrateMergeFailedEvent()
    ' Create a DataSet with one table containing two columns.
    Dim dataSet As New DataSet("dataSet")
    Dim table As New DataTable("Items")
    
    ' Add table to the DataSet.
    dataSet.Tables.Add(table)

    ' Add two columns to the DataTable.
    table.Columns.Add("id", Type.GetType("System.Int32"))
    table.Columns.Add("item", Type.GetType("System.Int32"))

    ' Set the primary key to the first column.
    table.PrimaryKey = new DataColumn() { table.Columns("id") }

    ' Add MergeFailed event handler for the table.
    AddHandler dataSet.MergeFailed, _
        New MergeFailedEventHandler(AddressOf Merge_Failed)

    ' Create a second DataTable identical to the first, 
    Dim t2 As DataTable = table.Clone()

    ' Set the primary key of the new table to the second column.
    ' This will cause the MergeFailed event to be raised when the
    ' table is merged into the DataSet.
    t2.PrimaryKey = New DataColumn() { t2.Columns("item") }
    
    ' Merge table into the DataSet.
    Console.WriteLine("Merging...")
    dataSet.Merge(t2, false, MissingSchemaAction.Add)
End Sub

Private Shared Sub Merge_Failed(sender As object, _
    e As MergeFailedEventArgs)
    Console.WriteLine("Merge_Failed Event: '{0}'", e.Conflict)
End Sub