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ObjectQuery<T>.UnionAll(ObjectQuery<T>) Method

  • Reference

Definition

Namespace:
System.Data.Objects
Assembly:
System.Data.Entity.dll

Combines the results of the query with the results of another object query, including all duplicates.

public:
 System::Data::Objects::ObjectQuery<T> ^ UnionAll(System::Data::Objects::ObjectQuery<T> ^ query);
public System.Data.Objects.ObjectQuery<T> UnionAll (System.Data.Objects.ObjectQuery<T> query);
member this.UnionAll : System.Data.Objects.ObjectQuery<'T> -> System.Data.Objects.ObjectQuery<'T>
Public Function UnionAll (query As ObjectQuery(Of T)) As ObjectQuery(Of T)

Parameters

query
ObjectQuery<T>

An ObjectQuery<T> that represents the results to add.

Returns

ObjectQuery<T>

A new ObjectQuery<T> instance that is equivalent to the original instance with UNION ALL applied to add the results of the specified query.

Exceptions

ArgumentNullException

The query parameter is null.

Examples

This example uses the UnionAll method to create a new ObjectQuery<T> object. Then it calls the Distinct method on the new ObjectQuery<T> object to get the unique results of this query.

int productID = 100;
using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    string queryString =
        @"SELECT VALUE product FROM AdventureWorksEntities.Products
            AS product WHERE product.ProductID < @productID";

    ObjectQuery<Product> productQuery =
        new ObjectQuery<Product>(queryString,
            context, MergeOption.NoTracking);

    ObjectQuery<Product> productQuery2 =
        new ObjectQuery<Product>(queryString,
            context, MergeOption.NoTracking);

    ObjectQuery<Product> productQuery3 =
        productQuery.UnionAll(productQuery2);

    productQuery3.Parameters.Add(new ObjectParameter("productID", productID));

    Console.WriteLine("Result of UnionAll");
    Console.WriteLine("------------------");

    // Iterate through the collection of Product items,
    // after the UnionAll method was called on two queries.
    foreach (Product result in productQuery3)
    {
        Console.WriteLine("Product Name: {0}", result.ProductID);
    }
    ObjectQuery<Product> productQuery4 = productQuery3.Distinct();

    Console.WriteLine("\nResult of Distinct");
    Console.WriteLine("------------------");

    // Iterate through the collection of Product items.
    // after the Distinct method was called on a query.
    foreach (Product result in productQuery4)
        Console.WriteLine("Product Name: {0}", result.ProductID);
}

Remarks

UnionAll adds the results of the supplied query including all duplicates.

The supplied query that defines results to add must be of the same type or of a type that can be promoted to the type of this ObjectQuery<T>. For example, the following is valid because DiscontinuedProducts can be promoted to Products:

ObjectQuery<Product>.Union(ObjectQuery<DiscontinuedProduct>)

The following will throw an exception because Products cannot be promoted to DiscontinuedProducts.

ObjectQuery <DiscontinuedProduct>.Union(ObjectQuery<Product>)

For an ObjectQuery<T> of type DbDataRecord, the records in both queries must have the same number of columns, and the types in the columns of the DbDataRecord of the passed query must be promotable to the types of the columns in the DbDataRecord of the ObjectQuery<T>.

Parameters that are defined in the supplied query are merged with parameters that are defined in the ObjectQuery<T> instance. Parameters must be unique in the combined ObjectParameterCollection. There cannot be two parameters in the combined collection with the same name. For more information, see Query Builder Methods.

The resulting query inherits the connection from the ObjectQuery<T> instance on which UnionAll was called.

Applies to

See also