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Expression.Coalesce Method (Expression, Expression, LambdaExpression)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Creates a BinaryExpression that represents a coalescing operation, given a conversion function.

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

Syntax

'Declaration
Public Shared Function Coalesce ( _
    left As Expression, _
    right As Expression, _
    conversion As LambdaExpression _
) As BinaryExpression

public static BinaryExpression Coalesce(
    Expression left,
    Expression right,
    LambdaExpression conversion
)

Parameters

Return Value

Type: System.Linq.Expressions.BinaryExpression
A BinaryExpression that has the NodeType property equal to Coalesce and the Left, Right and Conversion properties set to the specified values.

Exceptions

Exception Condition
ArgumentNullException

left or right is nulla null reference (Nothing in Visual Basic).
ArgumentException

left.Type and right.Type are not convertible to each other.

-or-

conversion is not nulla null reference (Nothing in Visual Basic) and conversion.Type is a delegate type that does not take exactly one argument.
InvalidOperationException

The Type property of left does not represent a reference type or a nullable value type.

-or-

The Type property of left represents a type that is not assignable to the parameter type of the delegate type conversion.Type.

-or-

The Type property of right is not equal to the return type of the delegate type conversion.Type.

Remarks

The Method property of the resulting BinaryExpression is nulla null reference (Nothing in Visual Basic) and both IsLifted and IsLiftedToNull are set to false.

The Type property of the resulting BinaryExpression is equal to the result type of the coalescing operation.

The following rules determine the result type:

  • If left.Type represents a nullable type and right.Type is implicitly convertible to the corresponding non-nullable type, the result type is the non-nullable equivalent of left.Type.

  • Otherwise, if right.Type is implicitly convertible to left.Type, the result type is left.Type.

  • Otherwise, if the non-nullable equivalent of left.Type is implicitly convertible to right.Type, the result type is right.Type.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.