ObjectQuery<T>.Select(String, ObjectParameter[]) Method

Definition

Namespace:

System.Data.Objects

Assembly:

System.Data.Entity.dll

Limits the query results to only the properties that are defined in the specified projection.

C#

public System.Data.Objects.ObjectQuery<System.Data.Common.DbDataRecord> Select(string projection, params System.Data.Objects.ObjectParameter[] parameters);

Parameters

projection

String

The list of selected properties that defines the projection.

parameters

ObjectParameter[]

Zero or more parameters that are used in this method.

Returns

ObjectQuery<DbDataRecord>

A new ObjectQuery<T> instance of type DbDataRecord that is equivalent to the original instance with SELECT applied.

Exceptions

ArgumentNullException

projection is null.

-or-

parameters is null.

ArgumentException

The projection is an empty string.

Examples

This example creates a new ObjectQuery<T> whose results are data records that contain the ProductID fields of the results of this query.

C#

int productID = 900;
using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    string queryString = @"SELECT VALUE product FROM
        AdventureWorksEntities.Products AS product
        WHERE product.ProductID > @productID";

    ObjectQuery<Product> productQuery1 =
        new ObjectQuery<Product>(queryString,
            context, MergeOption.NoTracking);

    productQuery1.Parameters.Add(new ObjectParameter("productID", productID));

    ObjectQuery<DbDataRecord> productQuery2 =
        productQuery1.Select("it.ProductID");

    foreach (DbDataRecord result in productQuery2)
    {
        Console.WriteLine("{0}", result["ProductID"]);
    }
}

Remarks

Select applies the projection specified by the projection parameter. The ObjectQuery<T> returned by the Select method is always a row type of DbDataRecord. Use the SelectValue method to return values that are simple types, entity types, or complex types. For more information, see LINQ to Entities.

When a navigation property is included in the projection, the query results include a collection of nested DbDataRecord objects.

Applies to

See also

• Querying Data as Objects (Entity Framework)