Expression.IfThen(Expression, Expression) Expression.IfThen(Expression, Expression) Expression.IfThen(Expression, Expression) Expression.IfThen(Expression, Expression) Method

定義

ConditionalExpression ステートメントを指定して、条件付きブロックを表す if を作成します。Creates a ConditionalExpression that represents a conditional block with an if statement.

public:
 static System::Linq::Expressions::ConditionalExpression ^ IfThen(System::Linq::Expressions::Expression ^ test, System::Linq::Expressions::Expression ^ ifTrue);
public static System.Linq.Expressions.ConditionalExpression IfThen (System.Linq.Expressions.Expression test, System.Linq.Expressions.Expression ifTrue);
static member IfThen : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression -> System.Linq.Expressions.ConditionalExpression
Public Shared Function IfThen (test As Expression, ifTrue As Expression) As ConditionalExpression

パラメーター

test
Expression Expression Expression Expression

Expression プロパティを等しく設定する TestAn Expression to set the Test property equal to.

ifTrue
Expression Expression Expression Expression

Expression プロパティを等しく設定する IfTrueAn Expression to set the IfTrue property equal to.

戻り値

ConditionalExpression と等しい NodeType プロパティと、指定した値に設定された Conditional プロパティおよび Test プロパティを含む IfTrueA ConditionalExpression that has the NodeType property equal to Conditional and the Test, IfTrue, properties set to the specified values. IfFalse プロパティは既定の式に設定されます。また、このメソッドによって返される結果の ConditionalExpression の型は Void です。The IfFalse property is set to default expression and the type of the resulting ConditionalExpression returned by this method is Void.

次のコード例では、条件付きブロックを表す式を作成する方法を示します。The following code example shows how to create an expression that represents a conditional block.

// Add the following directive to the file:
// using System.Linq.Expressions;  
bool test = true;

// This expression represents the conditional block.
Expression ifThenExpr = Expression.IfThen(
    Expression.Constant(test),
    Expression.Call(
        null,
        typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
        Expression.Constant("The condition is true.")
       )
);

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action>(ifThenExpr).Compile()();

// This code example produces the following output:
//
// The condition is true.
' Add the following directive to the file:
' Imports System.Linq.Expressions
Dim test As Boolean = True

' This expression represents the conditional block.
Dim ifThenExpr As Expression = Expression.IfThen(
     Expression.Constant(test),
     Expression.Call(
         Nothing,
         GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
         Expression.Constant("The condition is true.")
     )
)

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
Expression.Lambda(Of Action)(ifThenExpr).Compile()()

' This code example produces the following output:
'
' The condition is true.

適用対象