LoopExpression LoopExpression LoopExpression LoopExpression Class

Definition

Represents an infinite loop. It can be exited with "break".

public ref class LoopExpression sealed : System::Linq::Expressions::Expression
public sealed class LoopExpression : System.Linq.Expressions.Expression
type LoopExpression = class
    inherit Expression
Public NotInheritable Class LoopExpression
Inherits Expression
Inheritance
LoopExpressionLoopExpressionLoopExpressionLoopExpression

Examples

The following example demonstrates how to create a block expression that contains a LoopExpression object by using the Loop method.

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

// Creating a parameter expression.
ParameterExpression value = Expression.Parameter(typeof(int), "value");

// Creating an expression to hold a local variable. 
ParameterExpression result = Expression.Parameter(typeof(int), "result");

// Creating a label to jump to from a loop.
LabelTarget label = Expression.Label(typeof(int));

// Creating a method body.
BlockExpression block = Expression.Block(
    new[] { result },
    Expression.Assign(result, Expression.Constant(1)),
        Expression.Loop(
           Expression.IfThenElse(
               Expression.GreaterThan(value, Expression.Constant(1)),
               Expression.MultiplyAssign(result,
                   Expression.PostDecrementAssign(value)),
               Expression.Break(label, result)
           ),
       label
    )
);

// Compile and run an expression tree.
int factorial = Expression.Lambda<Func<int, int>>(block, value).Compile()(5);

Console.WriteLine(factorial);

// This code example produces the following output:
//
// 120
' Add the following directive to the file:
' Imports System.Linq.Expressions  
' Creating a parameter expression.
Dim value As ParameterExpression =
    Expression.Parameter(GetType(Integer), "value")

' Creating an expression to hold a local variable. 
Dim result As ParameterExpression =
    Expression.Parameter(GetType(Integer), "result")

' Creating a label to jump to from a loop.
Dim label As LabelTarget = Expression.Label(GetType(Integer))

' Creating a method body.
Dim block As BlockExpression = Expression.Block(
    New ParameterExpression() {result},
    Expression.Assign(result, Expression.Constant(1)),
    Expression.Loop(
        Expression.IfThenElse(
            Expression.GreaterThan(value, Expression.Constant(1)),
            Expression.MultiplyAssign(result,
                Expression.PostDecrementAssign(value)),
            Expression.Break(label, result)
        ),
        label
    )
)

' Compile an expression tree and return a delegate.
Dim factorial As Integer =
    Expression.Lambda(Of Func(Of Integer, Integer))(block, value).Compile()(5)

Console.WriteLine(factorial)

' This code example produces the following output:
'
' 120

Properties

Body Body Body Body

Gets the Expression that is the body of the loop.

BreakLabel BreakLabel BreakLabel BreakLabel

Gets the LabelTarget that is used by the loop body as a break statement target.

CanReduce CanReduce CanReduce 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)
ContinueLabel ContinueLabel ContinueLabel ContinueLabel

Gets the LabelTarget that is used by the loop body as a continue statement target.

NodeType NodeType NodeType NodeType

Returns the node type of this expression. Extension nodes should return Extension when overriding this method.

Type Type Type Type

Gets the static type of the expression that this Expression represents.

Methods

Accept(ExpressionVisitor) Accept(ExpressionVisitor) Accept(ExpressionVisitor) Accept(ExpressionVisitor)

Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall(MethodCallExpression).

(Inherited from Expression)
Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
Reduce() Reduce() Reduce() 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() ReduceAndCheck() ReduceAndCheck() 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() ReduceExtensions() ReduceExtensions() 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() ToString() ToString() ToString()

Returns a textual representation of the Expression.

(Inherited from Expression)
Update(LabelTarget, LabelTarget, Expression) Update(LabelTarget, LabelTarget, Expression) Update(LabelTarget, LabelTarget, Expression) Update(LabelTarget, LabelTarget, Expression)

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(ExpressionVisitor) VisitChildren(ExpressionVisitor) VisitChildren(ExpressionVisitor) 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)

Applies to