Expression.Coalesce Method (Expression, Expression, LambdaExpression)

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

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

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

Parameters

left
Type: System.Linq.Expressions.Expression

An Expression to set the Left property equal to.

right
Type: System.Linq.Expressions.Expression

An Expression to set the Right property equal to.

conversion
Type: System.Linq.Expressions.LambdaExpression

A LambdaExpression to set the Conversion property equal to.

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.

ExceptionCondition
ArgumentNullException

left or right is null.

ArgumentException

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

-or-

conversion is not null 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.

The Method property of the resulting BinaryExpression is null 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.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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