LambdaExpression Class

Definition

Namespace:

System.Linq.Expressions

Assembly:

System.Linq.Expressions.dll

Source:

LambdaExpression.cs

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

public ref class LambdaExpression abstract : System::Linq::Expressions::Expression

public abstract class LambdaExpression : System.Linq.Expressions.Expression

type LambdaExpression = class
    inherit Expression

Public MustInherit Class LambdaExpression
Inherits Expression

Inheritance

Object

Expression

LambdaExpression

Derived

System.Linq.Expressions.Expression<TDelegate>

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:
// 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.
Console.WriteLine(lambdaExpr);

// Compile and run the lamda expression.
// The value of the parameter is 1.
Console.WriteLine(lambdaExpr.Compile().DynamicInvoke(1));

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

' 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.
Console.WriteLine(lambdaExpr)

' Compile and run the lamda expression.
' The value of the parameter is 1.
Console.WriteLine(lambdaExpr.Compile().DynamicInvoke(1))

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

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.

Properties

Body	Gets the body of the lambda expression.
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)
Name	Gets the name of the lambda expression.
NodeType	Returns the node type of this Expression.
Parameters	Gets the parameters of the lambda expression.
ReturnType	Gets the return type of the lambda expression.
TailCall	Gets the value that indicates if the lambda expression will be compiled with the tail call optimization.
Type	Gets the static type of the expression that this Expression represents.

Methods

Accept(ExpressionVisitor)	Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall(MethodCallExpression). (Inherited from Expression)
Compile()	Produces a delegate that represents the lambda expression.
Compile(Boolean)	Produces an interpreted or compiled delegate that represents the lambda expression.
Compile(DebugInfoGenerator)	Produces a delegate that represents the lambda expression.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (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)
VisitChildren(ExpressionVisitor)	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)