UnionNode Class

A node that provides data with a Union and UnionAll queries.

Namespace : DevExpress.DataAccess.DataFederation

Assembly : DevExpress.DataAccess.v25.2.dll

NuGet Package : DevExpress.DataAccess

Declaration

C#
VB.NET

csharp

public class UnionNode :
    QueryNode

Public Class UnionNode
    Inherits QueryNode

The following members return UnionNode objects:

Remarks

The main part of the Federated Data Source is the FederationDataSourceBase.Queries collection that contains federated queries.

You can create federated queries of the following types:

Join
Union and Union All
Transformation

Add the UnionNode objects to the FederationDataSourceBase.Queries collection to use the created query in a federated data source.

The following code shows how to create Union and UnionAll queries and combine two Excel data sources:

C#
VB.NET

csharp

private static FederationDataSource CreateFederatedDataSourceUnion(SqlDataSource sqliteDataSource, ExcelDataSource exceldataSource) {
    FederationDataSource federationDS = new FederationDataSource();
    Source sqlSource = new Source("sqlite", sqliteDataSource, "SQLite Orders");
    Source excelSource = new Source("excel", exceldataSource);

    UnionNode queryUnionAll = sqlSource.From().Select("OrderID", "OrderDate").Build("OrdersSqlite")
        .UnionAll(excelSource.From().Select("OrderID", "OrderDate").Build("OrdersExcel"))
        .Build("OrdersUnionAll");

    UnionNode queryUnion = sqlSource.From().Select("OrderID", "OrderDate").Build("OrdersSqlite")
        .Union(excelSource.From().Select("OrderID", "OrderDate").Build("OrdersExcel"))
        .Build("OrdersUnion");

    federationDS.Queries.Add(queryUnionAll);
    federationDS.Queries.Add(queryUnion);

    federationDS.Fill(new DevExpress.Data.IParameter[0]);
    return federationDS;
}

Private Shared Function CreateFederatedDataSourceUnion(ByVal sqliteDataSource As SqlDataSource, ByVal exceldataSource As ExcelDataSource) As FederationDataSource
  Dim federationDS As New FederationDataSource()
  Dim sqlSource As New Source("sqlite", sqliteDataSource, "SQLite Orders")
  Dim excelSource As New Source("excel", exceldataSource)

  Dim queryUnionAll As UnionNode = sqlSource.From().Select("OrderID", "OrderDate").Build("OrdersSqlite").UnionAll(excelSource.From().Select("OrderID", "OrderDate").Build("OrdersExcel")).Build("OrdersUnionAll")

  Dim queryUnion As UnionNode = sqlSource.From().Select("OrderID", "OrderDate").Build("OrdersSqlite").Union(excelSource.From().Select("OrderID", "OrderDate").Build("OrdersExcel")).Build("OrdersUnion")

  federationDS.Queries.Add(queryUnionAll)
  federationDS.Queries.Add(queryUnion)

  federationDS.Fill(New DevExpress.Data.IParameter(){})
  Return federationDS
End Function