ConditionalExpression Класс

Определение

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

Наследование

Object

Expression

ConditionalExpression

Примеры

В следующем примере кода показано, как создать выражение, представляющее условную инструкцию. Если первый аргумент оценивается true, второй аргумент выполняется; в противном случае выполняется третий аргумент.

// 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

Комментарии

Используйте метод фабрики Condition для создания ConditionalExpression.

NodeType ConditionalExpressionЕсть Conditional .