VB.net Data Relation Creation

I found the following example of creating a Data Relation. I get the error DataSet1 is not declared
What additional code do I need

http://msdn.microsoft.com/en-us/library/system.data.datarelation(v=vs.110).aspx

    Private Sub CreateRelation()
        ' Get the DataColumn objects from two DataTable objects  
        ' in a DataSet. Code to get the DataSet not shown here.
        Dim parentColumn As DataColumn = _
            DataSet1.Tables("Customers").Columns("CustID")
        Dim childColumn As DataColumn = DataSet1.Tables( _
            "Orders").Columns("CustID")

        ' Create DataRelation.
        Dim relCustOrder As DataRelation
        relCustOrder = New DataRelation( _
            "CustomersOrders", parentColumn, childColumn)

        ' Add the relation to the DataSet.
        DataSet1.Relations.Add(relCustOrder)
    End Sub