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LambdaExpression Class

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Describes a lambda expression. This captures a block of code that is similar to a .NET method body.

Inheritance Hierarchy

System.Object
  System.Linq.Expressions.Expression
    System.Linq.Expressions.LambdaExpression
      System.Linq.Expressions.Expression<TDelegate>

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

Syntax

'Declaration
Public MustInherit Class LambdaExpression _
    Inherits Expression

public abstract class LambdaExpression : Expression

The LambdaExpression type exposes the following members.

Properties

  Name Description
Public propertySupported by Silverlight for Windows Phone Body Gets the body of the lambda expression.
Public property 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.)
Public property Name Gets the name of the lambda expression.
Public propertySupported by Silverlight for Windows Phone 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.
Public propertySupported by Silverlight for Windows Phone Parameters Gets the parameters of the lambda expression.
Public property ReturnType Gets the return type of the lambda expression.
Public property TailCall Gets the value that indicates if the lambda expression will be compiled with the tail call optimization.
Public propertySupported by Silverlight for Windows Phone 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
Protected method Accept Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Inherited from Expression.)
Public methodSupported by Silverlight for Windows Phone Compile() Produces a delegate that represents the lambda expression.
Public method Compile(DebugInfoGenerator) Produces a delegate that represents the lambda expression.
Public method CompileToMethod(MethodBuilder) Compiles the lambda into a method definition.
Public method CompileToMethod(MethodBuilder, DebugInfoGenerator) Compiles the lambda into a method definition and custom debug information.
Public methodSupported by Silverlight for Windows Phone Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows Phone 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.)
Public methodSupported by Silverlight for Windows Phone GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone GetType Gets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows Phone MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method 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.)
Public method 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.)
Public method 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.)
Public methodSupported by Silverlight for Windows Phone ToString Returns a textual representation of the Expression. (Inherited from Expression.)
Protected method 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

The LambdaExpression type represents a lambda expression in the form of an expression tree. The Expression<TDelegate> type, which derives from LambdaExpression and captures the type of the lambda expression more explicitly, can also be used to represent a lambda expression. At runtime, an expression tree node that represents a lambda expression is always of type Expression<TDelegate>.

The value of the NodeType property of a LambdaExpression is Lambda.

Use the Lambda factory methods to create a LambdaExpression object.

Examples

The following example demonstrates how to create an expression that represents a lambda expression that adds 1 to the passed argument by using the Lambda method.

' Add the following directive to your file:
' Imports System.Linq.Expressions  

' A parameter for the lambda expression.
Dim paramExpr As ParameterExpression = Expression.Parameter(GetType(Integer), "arg")

' This expression represents a lambda expression
' that adds 1 to the parameter value.
Dim lambdaExpr As LambdaExpression = Expression.Lambda(
        Expression.Add(
            paramExpr,
            Expression.Constant(1)
        ),
        New List(Of ParameterExpression)() From {paramExpr}
    )

' Print out the expression.
outputBlock.Text &= lambdaExpr.ToString() & vbCrLf

' Compile and run the lamda expression.
' The value of the parameter is 1.
outputBlock.Text &= lambdaExpr.Compile().DynamicInvoke(1).ToString() & vbCrLf

' This code example produces the following output:
'
' arg => (arg +1)
' 2

// Add the following directive to your file:
// using System.Linq.Expressions;  

// A parameter for the lambda expression.
ParameterExpression paramExpr = Expression.Parameter(typeof(int), "arg");

// This expression represents a lambda expression
// that adds 1 to the parameter value.
LambdaExpression lambdaExpr = Expression.Lambda(
    Expression.Add(
        paramExpr,
        Expression.Constant(1)
    ),
    new List<ParameterExpression>() { paramExpr }
);

// Print out the expression.
outputBlock.Text += lambdaExpr + "\n";

// Compile and run the lamda expression.
// The value of the parameter is 1.
outputBlock.Text += lambdaExpr.Compile().DynamicInvoke(1) + "\n";

// This code example produces the following output:
//
// arg => (arg +1)
// 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.