Expression.Coalesce Method (Expression, Expression, LambdaExpression)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Creates a BinaryExpression that represents a coalescing operation, given a conversion function.
Assembly: System.Core (in System.Core.dll)
'Declaration Public Shared Function Coalesce ( _ left As Expression, _ right As Expression, _ conversion As LambdaExpression _ ) As BinaryExpression
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.BinaryExpressionA BinaryExpression that has the NodeType property equal to Coalesce and the Left, Right and Conversion properties set to the specified values.
| Exception | Condition |
|---|---|
| ArgumentNullException | left or right is Nothing. |
| ArgumentException | left.Type and right.Type are not convertible to each other. -or- conversion is not Nothing 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 Nothing 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.