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Expression.Coalesce Method (Expression, Expression)

Creates a BinaryExpression that represents a coalescing operation.

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

public static BinaryExpression Coalesce(
	Expression left,
	Expression right


Type: System.Linq.Expressions.Expression
An Expression to set the Left property equal to.
Type: System.Linq.Expressions.Expression
An Expression to set the Right property equal to.

Return Value

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


left or right is null.


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


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

The Method property of the resulting BinaryExpression is null and both IsLifted and IsLiftedToNull are set to false. The Type property is equal to the result type of the coalescing operation. The Conversion property is null.

Result Type

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, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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