Freigeben über

  • Artikel

Expression.Negate Method (Expression)

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

Creates a UnaryExpression that represents an arithmetic negation operation.

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

Syntax

'Declaration
Public Shared Function Negate ( _
    expression As Expression _
) As UnaryExpression

public static UnaryExpression Negate(
    Expression expression
)

Parameters

Return Value

Type: System.Linq.Expressions.UnaryExpression
A UnaryExpression that has the NodeType property equal to Negate and the Operand property set to the specified value.

Exceptions

Exception Condition
ArgumentNullException

expression is nulla null reference (Nothing in Visual Basic).
InvalidOperationException

The unary minus operator is not defined for expression.Type.

Remarks

The Method property of the resulting UnaryExpression is set to the implementing method. The Type property is set to the type of the node. If the node is lifted, the IsLifted and IsLiftedToNull properties are both true. Otherwise, they are false.

Implementing Method

The following rules determine the implementing method for the operation:

  • If expression.Type is a user-defined type that defines the unary minus operator, the MethodInfo that represents that operator is the implementing method.

  • Otherwise, if expression.Type is a numeric type, the implementing method is nulla null reference (Nothing in Visual Basic).

Node Type and Lifted versus Non-Lifted

If the implementing method is not nulla null reference (Nothing in Visual Basic):

  • If expression.Type is assignable to the argument type of the implementing method, the node is not lifted. The type of the node is the return type of the implementing method.

  • If the following two conditions are satisfied, the node is lifted and the type of the node is the nullable type that corresponds to the return type of the implementing method:

    • expression.Type is a nullable value type and the corresponding non-nullable value type is equal to the argument type of the implementing method.

    • The return type of the implementing method is a non-nullable value type.

If the implementing method is nulla null reference (Nothing in Visual Basic), the type of the node is expression.Type. If expression.Type is non-nullable, the node is not lifted. Otherwise, the node is lifted.

Examples

The following example demonstrates how to create an expression that represents an arithmetic negation operation.

' Add the following directive to your file:
' Imports System.Linq.Expressions 

' This expression represents a negation operation.
Dim negateExpr As Expression = Expression.Negate(Expression.Constant(5))

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
outputBlock.Text &= Expression.Lambda(Of Func(Of Integer))(negateExpr).Compile()() & vbCrLf

' This code example produces the following output:
'
' -5

       // Add the following directive to your file:
       // using System.Linq.Expressions; 

       // This expression represents a negation operation.
       Expression negateExpr = Expression.Negate(Expression.Constant(5));

       // The following statement first creates an expression tree,
       // then compiles it, and then runs it.
       outputBlock.Text += Expression.Lambda<Func<int>>(negateExpr).Compile()() + "\n";

       // This code example produces the following output:
       //
       // -5

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.