项目
11/18/2011

MethodCallExpression Class

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

Represents a call to either static or an instance method.

Inheritance Hierarchy

System.Object
System.Linq.Expressions.Expression
System.Linq.Expressions.MethodCallExpression

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

Syntax

'Declaration
Public Class MethodCallExpression _
    Inherits Expression

public class MethodCallExpression : Expression

The MethodCallExpression type exposes the following members.

Properties

	Name	Description
	Arguments	Gets a collection of expressions that represent arguments of the called method.
	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.)
	Method	Gets the MethodInfo for the method to be called.
	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.
	Object	Gets the Expression that represents the instance for instance method calls or null for static method calls.
	Type	Gets the static type of the expression that this Expression represents. (Overrides Expression.Type.) In Silverlight for Windows Phone Windows Phone OS 7.1, this member is inherited from Expression.Type. In XNA Framework Windows Phone OS 7.0, this member is inherited from Expression.Type.

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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 Call, ArrayIndex, or ArrayIndex factory method to create a MethodCallExpression.

The value of the NodeType property of a MethodCallExpression object is Call.

Examples

The following example creates a MethodCallExpression object that represents indexing into a two-dimensional array.

Dim gradeArray(,) As String = _
    {{"chemistry", "history", "mathematics"}, {"78", "61", "82"}}

Dim arrayExpression As System.Linq.Expressions.Expression = _
    System.Linq.Expressions.Expression.Constant(gradeArray)

' Create a MethodCallExpression that represents indexing
' into the two-dimensional array 'gradeArray' at (0, 2).
' Executing the expression would return "mathematics".
Dim methodCallExpression As System.Linq.Expressions.MethodCallExpression = _
    System.Linq.Expressions.Expression.ArrayIndex( _
        arrayExpression, _
        System.Linq.Expressions.Expression.Constant(0), _
        System.Linq.Expressions.Expression.Constant(2))

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

' This code produces the following output:
'
' value(System.String[,]).Get(0, 2)

string[,] gradeArray = { { "chemistry", "history", "mathematics" }, { "78", "61", "82" } };

System.Linq.Expressions.Expression arrayExpression =
    System.Linq.Expressions.Expression.Constant(gradeArray);

// Create a MethodCallExpression that represents indexing
// into the two-dimensional array 'gradeArray' at (0, 2).
// Executing the expression would return "mathematics".
System.Linq.Expressions.MethodCallExpression methodCallExpression =
    System.Linq.Expressions.Expression.ArrayIndex(
        arrayExpression,
        System.Linq.Expressions.Expression.Constant(0),
        System.Linq.Expressions.Expression.Constant(2));

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

// This code produces the following output:
//
// value(System.String[,]).Get(0, 2)

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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