Статья
11/18/2011

MemberExpression Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Represents accessing a field or property.

Inheritance Hierarchy

System.Object
System.Linq.Expressions.Expression
System.Linq.Expressions.MemberExpression

Namespace: System.Linq.Expressions
Assembly: System.Core (in System.Core.dll)

Syntax

'Declaration
Public Class MemberExpression _
    Inherits Expression

public class MemberExpression : Expression

The MemberExpression type exposes the following members.

Properties

	Name	Description
	CanReduce	Indicates that the node can be reduced to a simpler node. If this returns true, Reduce() can be called to produce the reduced form. (Inherited from Expression.)
	Expression	Gets the containing object of the field or property.
	Member	Gets the field or property to be accessed.
	NodeType	Returns the node type of this Expression. (Overrides Expression.NodeType.) In Silverlight for Windows Phone Windows Phone OS 7.1, this member is inherited from Expression.NodeType. In XNA Framework Windows Phone OS 7.0, this member is inherited from Expression.NodeType.
	Type	Gets the static type of the expression that this Expression represents. (Inherited from Expression.)

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Methods

	Name	Description
	Accept	Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Overrides Expression.Accept(ExpressionVisitor).)
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Reduce	Reduces this node to a simpler expression. If CanReduce returns true, this should return a valid expression. This method can return another node which itself must be reduced. (Inherited from Expression.)
	ReduceAndCheck	Reduces this node to a simpler expression. If CanReduce returns true, this should return a valid expression. This method can return another node which itself must be reduced. (Inherited from Expression.)
	ReduceExtensions	Reduces the expression to a known node type (that is not an Extension node) or just returns the expression if it is already a known type. (Inherited from Expression.)
	ToString	Returns a textual representation of the Expression. (Inherited from Expression.)
	Update	Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
	VisitChildren	Reduces the node and then calls the visitor delegate on the reduced expression. The method throws an exception if the node is not reducible. (Inherited from Expression.)

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Remarks

Use the Field, Property or PropertyOrField factory methods to create a MemberExpression.

The value of the NodeType property of a MemberExpression is MemberAccess.

Examples

The following example creates a MemberExpression that represents getting the value of a field member.

Class Animal
   Dim species As String
End Class

Public Sub CreateFieldExpression()
   Dim horse As New Animal

   ' Create a MemberExpression that represents getting
   ' the value of the 'species' field of class 'Animal'.
   Dim memberExpression As System.Linq.Expressions.MemberExpression = _
       System.Linq.Expressions.Expression.Field( _
           System.Linq.Expressions.Expression.Constant(horse), _
           "species")

   outputBlock.Text &= memberExpression.ToString() & vbCrLf

   ' This code produces the following output:
   '
   ' value(ExpressionVB.FieldExample+Animal).species
End Sub

class Animal
{
   public string species = null;
}

public void CreateFieldExpression()
{
   Animal horse = new Animal();

   // Create a MemberExpression that represents getting
   // the value of the 'species' field of class 'Animal'.
   System.Linq.Expressions.MemberExpression memberExpression =
       System.Linq.Expressions.Expression.Field(
           System.Linq.Expressions.Expression.Constant(horse),
           "species");

   outputBlock.Text += memberExpression.ToString() + "\n";

   // This code produces the following output:
   //
   // value(CodeSnippets.FieldExample+Animal).species
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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