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

 

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

Namespace:   System.Data.Objects
Assembly:  System.Data.Entity (in System.Data.Entity.dll)

public ObjectQuery<DbDataRecord> Select(
	string projection,
	params ObjectParameter[] parameters
)

Parameters

projection
Type: System.String

The list of selected properties that defines the projection.

parameters
Type: System.Data.Objects.ObjectParameter[]

Zero or more parameters that are used in this method.

Return Value

Type: System.Data.Objects.ObjectQuery<DbDataRecord>

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

Exception Condition
ArgumentNullException

projection is null.

-or-

parameters is null.

ArgumentException

The projection is an empty string.

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<TResultType> method to return values that are simple types, entity types, or complex types. For more information, see Object Queries.

When a navigation property is included in the projection, the query results include a collection of nested DbDataRecord objects. For more information, see How to: Navigate Relationships Using Navigation Properties.

This example is based on the AdventureWorks Sales Model. The example creates a new ObjectQuery<T> whose results are data records that contain the ProductID fields of the results of this query.

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"]);
    }
}

.NET Framework
Available since 3.5
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