ConditionalExpression Classe

Définition

public ref class ConditionalExpression : System::Linq::Expressions::Expression

public ref class ConditionalExpression sealed : System::Linq::Expressions::Expression

public class ConditionalExpression : System.Linq.Expressions.Expression

public sealed class ConditionalExpression : System.Linq.Expressions.Expression

type ConditionalExpression = class
    inherit Expression

Public Class ConditionalExpression
Inherits Expression

Public NotInheritable Class ConditionalExpression
Inherits Expression

Héritage

Object

Expression

ConditionalExpression

Exemples

L’exemple de code suivant montre comment créer une expression qui représente une instruction conditionnelle. Si le premier argument est évalué trueà , le deuxième argument est exécuté ; sinon, le troisième argument est exécuté.

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

int num = 100;

// This expression represents a conditional operation.
// It evaluates the test (first expression) and
// executes the iftrue block (second argument) if the test evaluates to true,
// or the iffalse block (third argument) if the test evaluates to false.
Expression conditionExpr = Expression.Condition(
                           Expression.Constant(num > 10),
                           Expression.Constant("num is greater than 10"),
                           Expression.Constant("num is smaller than 10")
                         );

// Print out the expression.
Console.WriteLine(conditionExpr.ToString());

// The following statement first creates an expression tree,
// then compiles it, and then executes it.
Console.WriteLine(
    Expression.Lambda<Func<string>>(conditionExpr).Compile()());

// This code example produces the following output:
//
// IIF("True", "num is greater than 10", "num is smaller than 10")
// num is greater than 10

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

Dim num As Integer = 100

' This expression represents a conditional operation; 
' it will evaluate the test (first expression) and
' execute the ifTrue block (second argument) if the test evaluates to true, 
' or the ifFalse block (third argument) if the test evaluates to false.
Dim conditionExpr As Expression = Expression.Condition(
                            Expression.Constant(num > 10),
                            Expression.Constant("n is greater than 10"),
                            Expression.Constant("n is smaller than 10")
                        )

' Print the expression.
Console.WriteLine(conditionExpr.ToString())

' The following statement first creates an expression tree,
' then compiles it, and then executes it.       
Console.WriteLine(
    Expression.Lambda(Of Func(Of String))(conditionExpr).Compile()())

' This code example produces the following output:
'
' IIF("True", "num is greater than 10", "num is smaller than 10")
' num is greater than 10

Remarques

Utilisez la Condition méthode de fabrique pour créer un ConditionalExpression.

Le NodeType d’un ConditionalExpression est Conditional.