LoopExpression Class
Definition
Important
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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
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 |
Gets the Expression that is the body of the loop. |
BreakLabel |
Gets the LabelTarget that is used by the loop body as a break statement target. |
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 |
Gets the LabelTarget that is used by the loop body as a continue statement target. |
NodeType |
Returns the node type of this expression. Extension nodes should return Extension when overriding this method. |
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) |
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) |
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) |
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) |