DbExpressionBuilder.Select<TProjection> Method

Reference

Definition

Namespace:: System.Data.Common.CommandTrees.ExpressionBuilder

Assembly:: System.Data.Entity.dll

Important

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Creates a new DbProjectExpression that selects the specified expression over the given input set.

public:
generic <typename TProjection>
[System::Runtime::CompilerServices::Extension]
 static System::Data::Common::CommandTrees::DbProjectExpression ^ Select(System::Data::Common::CommandTrees::DbExpression ^ source, Func<System::Data::Common::CommandTrees::DbExpression ^, TProjection> ^ projection);

public static System.Data.Common.CommandTrees.DbProjectExpression Select<TProjection>(this System.Data.Common.CommandTrees.DbExpression source, Func<System.Data.Common.CommandTrees.DbExpression,TProjection> projection);

static member Select : System.Data.Common.CommandTrees.DbExpression * Func<System.Data.Common.CommandTrees.DbExpression, 'Projection> -> System.Data.Common.CommandTrees.DbProjectExpression

<Extension()>
Public Function Select(Of TProjection) (source As DbExpression, projection As Func(Of DbExpression, TProjection)) As DbProjectExpression

Type Parameters

TProjection

The method result type of projection.

Parameters

source: DbExpression

An expression that specifies the input set.

projection: Func<DbExpression,TProjection>

A method that specifies how to derive the projected expression given a member of the input set. This method must produce an instance of a type that is compatible with Select and can be resolved into a DbExpression. Compatibility requirements for TProjection are described in remarks.

Returns

DbProjectExpression

A new DbProjectExpression that represents the select operation.

Exceptions

ArgumentNullException

source or projection is null.

-or-

The result of projection is null.

Remarks

To be compatible with Select, TProjection must be derived from DbExpression, or must be an anonymous type with DbExpression-derived properties. The following are examples of supported types for TProjection:

source.Select(x => x.Property("Name"))

TProjection is DbPropertyExpression).

source.Select(x => new { Name = x.Property("Name") })

(TProjection is an anonymous type with a DbExpression-derived property).

Applies to

Продукт	Версии
.NET Framework	4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1

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