public sealed class Source

Public NotInheritable Class Source

using DevExpress.DataAccess.DataFederation;
// ...
    FederationDataSource federation = new FederationDataSource();

    Source sourceProducts = new Source("Products", CreateSqlDataSource(), "Products");
    Source sourceOrderDetail = new Source("OrderDetail", CreateExcelDataSource("SalesPerson.xlsx", "Data"));
    Source sourceHeader = new Source("OrderHeader", CreateExcelDataSource("OrderHeaders.xlsx", "OrderHeader"));

    SelectNode query1 = sourceProducts.From().Select("ProductName", "QuantityPerUnit", "UnitsInStock")
        .Join(sourceOrderDetail, "[Products.ProductName] = [OrderDetail.ProductName]")
        .Select("OrderDate")
        .Build("ProductsOrderDetail");

    SelectNode query2 = sourceHeader.From().Select("OrderID", "Status", "Description")
        .Join(sourceOrderDetail, "[OrderHeader.OrderID] = [OrderDetail.OrderID]")
        .Select("Quantity", "Extended Price")
        .Build("OrderHeaderOrderDetail");

    federation.Queries.AddRange(new[] { query1, query2 });
    federation.Fill()

Imports DevExpress.DataAccess.DataFederation
' ... 
    Dim federation As New FederationDataSource()

    Dim sourceProducts As New Source("Products", CreateSqlDataSource(), "Products")
    Dim sourceOrderDetail As New Source("OrderDetail", CreateExcelDataSource("SalesPerson.xlsx", "Data"))
    Dim sourceHeader As New Source("OrderHeader", CreateExcelDataSource("OrderHeaders.xlsx", "OrderHeader"))

    Dim query1 As SelectNode = sourceProducts.From().
        Select("ProductName", "QuantityPerUnit", "UnitsInStock").
        Join(sourceOrderDetail, "[Products.ProductName] = [OrderDetail.ProductName]").
        Select("OrderDate").
        Build("ProductsOrderDetail")

    Dim query2 As SelectNode = sourceHeader.From().
        Select("OrderID", "Status", "Description").
        Join(sourceOrderDetail, "[OrderHeader.OrderID] = [OrderDetail.OrderID]").
        Select("Quantity", "Extended Price").
        Build("OrderHeaderOrderDetail")

    federation.Queries.AddRange( { query1, query2 })
    federation.Fill()