ConditionalExpression Třída

Definice

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

Dědičnost

Object

Expression

ConditionalExpression

Příklady

Následující příklad kódu ukazuje, jak vytvořit výraz, který představuje podmíněný příkaz. Pokud se první argument vyhodnotí jako , provede se truedruhý argument; v opačném případě se provede třetí argument.

// 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

Poznámky

K vytvoření objektu Condition použijte metodu ConditionalExpressionfactory .

Hodnota NodeType je ConditionalExpressionConditional.

Vlastnosti

Metody

Platí pro