Expression.Condition Metod

public:
 static System::Linq::Expressions::ConditionalExpression ^ Condition(System::Linq::Expressions::Expression ^ test, System::Linq::Expressions::Expression ^ ifTrue, System::Linq::Expressions::Expression ^ ifFalse);

public static System.Linq.Expressions.ConditionalExpression Condition(System.Linq.Expressions.Expression test, System.Linq.Expressions.Expression ifTrue, System.Linq.Expressions.Expression ifFalse);

static member Condition : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Linq.Expressions.Expression -> System.Linq.Expressions.ConditionalExpression

Public Shared Function Condition (test As Expression, ifTrue As Expression, ifFalse As Expression) As ConditionalExpression

Parametrar

Returer

En ConditionalExpression som har NodeType egenskapen lika med Conditional och Testegenskaperna , IfTrueoch IfFalse som är inställda på de angivna värdena.

Undantag

Exempel

I följande kodexempel visas hur du skapar ett uttryck som representerar en villkorssats. Om det första argumentet utvärderas till truekörs det andra argumentet. Annars körs det tredje argumentet.

// 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

Kommentarer

Egenskapen Type för resultatet ConditionalExpression är lika med Type egenskapen ifTrueför .

Se även

• IfThen(Expression, Expression)
• IfThenElse(Expression, Expression, Expression)

public:
 static System::Linq::Expressions::ConditionalExpression ^ Condition(System::Linq::Expressions::Expression ^ test, System::Linq::Expressions::Expression ^ ifTrue, System::Linq::Expressions::Expression ^ ifFalse, Type ^ type);

public static System.Linq.Expressions.ConditionalExpression Condition(System.Linq.Expressions.Expression test, System.Linq.Expressions.Expression ifTrue, System.Linq.Expressions.Expression ifFalse, Type type);

static member Condition : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * Type -> System.Linq.Expressions.ConditionalExpression

Public Shared Function Condition (test As Expression, ifTrue As Expression, ifFalse As Expression, type As Type) As ConditionalExpression

Parametrar

Returer

En ConditionalExpression som har NodeType egenskapen lika med Conditional och Testegenskaperna , IfTrueoch IfFalse som är inställda på de angivna värdena.

Kommentarer

Med den här metoden kan du explicit ena resultattypen för villkorsuttrycket i fall där typerna av ifTrue och ifFalse uttrycken inte är lika. Typer av båda ifTrue och ifFalse måste implicit referera till tilldelningsbara till resultattypen. Tillåts type vara Void.