Expression.Condition Metoda

Zdroj:

ConditionalExpression.cs

Zdroj:

ConditionalExpression.cs

Zdroj:

ConditionalExpression.cs

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

Parametry

Návraty

Vlastnost , ConditionalExpression která má NodeType vlastnost , IfTrueConditionalTesta IfFalse nastavené na zadané hodnoty.

Výjimky

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

Vlastnost Type výsledného ConditionalExpression objektu Type se rovná vlastnosti objektu ifTrue.

Viz také

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

Zdroj:

ConditionalExpression.cs

Zdroj:

ConditionalExpression.cs

Zdroj:

ConditionalExpression.cs

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

Parametry

Návraty

Vlastnost , ConditionalExpression která má NodeType vlastnost , IfTrueConditionalTesta IfFalse nastavené na zadané hodnoty.

Poznámky

Tato metoda umožňuje explicitně sjednotit typ výsledku podmíněného výrazu v případech, kdy se typy výrazů ifTrue a ifFalse nerovnají. Typy a ifTrueifFalse musí být implicitně odkazovatelné na typ výsledku. Hodnota type může být Void.