Expression.Condition Method (Expression, Expression, Expression)

 

Creates a ConditionalExpression that represents a conditional statement.

Namespace:   System.Linq.Expressions
Assembly:  System.Core (in System.Core.dll)

public static ConditionalExpression Condition(
	Expression test,
	Expression ifTrue,
	Expression ifFalse
)

Parameters

test
Type: System.Linq.Expressions.Expression

An Expression to set the Test property equal to.

ifTrue
Type: System.Linq.Expressions.Expression

An Expression to set the IfTrue property equal to.

ifFalse
Type: System.Linq.Expressions.Expression

An Expression to set the IfFalse property equal to.

Return Value

Type: System.Linq.Expressions.ConditionalExpression

A ConditionalExpression that has the NodeType property equal to Conditional and the Test, IfTrue, and IfFalse properties set to the specified values.

Exception Condition
ArgumentNullException

test or ifTrue or ifFalse is null.

ArgumentException

test.Type is not Boolean.

-or-

ifTrue.Type is not equal to ifFalse.Type.

The Type property of the resulting ConditionalExpression is equal to the Type property of ifTrue.

The following code example shows how to create an expression that represents a conditional statement. If the first argument evaluates to true, the second argument is executed; otherwise, the third argument is executed.

// 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

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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