Expression.Negate Method

Definition

Namespace:

System.Linq.Expressions

Assembly:

System.Linq.Expressions.dll

Creates a UnaryExpression that represents an arithmetic negation operation.

Overloads

Negate(Expression, MethodInfo)	Creates a UnaryExpression that represents an arithmetic negation operation.
Negate(Expression)	Creates a UnaryExpression that represents an arithmetic negation operation.

Negate(Expression, MethodInfo)

Source:

UnaryExpression.cs

Creates a UnaryExpression that represents an arithmetic negation operation.

public:
 static System::Linq::Expressions::UnaryExpression ^ Negate(System::Linq::Expressions::Expression ^ expression, System::Reflection::MethodInfo ^ method);

public static System.Linq.Expressions.UnaryExpression Negate (System.Linq.Expressions.Expression expression, System.Reflection.MethodInfo? method);

static member Negate : System.Linq.Expressions.Expression * System.Reflection.MethodInfo -> System.Linq.Expressions.UnaryExpression

Public Shared Function Negate (expression As Expression, method As MethodInfo) As UnaryExpression

Parameters

expression

Expression

An Expression to set the Operand property equal to.

method

MethodInfo

A MethodInfo to set the Method property equal to.

Returns

UnaryExpression

A UnaryExpression that has the NodeType property equal to Negate and the Operand and Method properties set to the specified values.

Exceptions

ArgumentNullException

expression is null.

ArgumentException

method is not null and the method it represents returns void, is not static (Shared in Visual Basic), or does not take exactly one argument.

InvalidOperationException

method is null and the unary minus operator is not defined for expression.Type.

-or-

expression.Type (or its corresponding non-nullable type if it is a nullable value type) is not assignable to the argument type of the method represented by method.

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 method is not null and it represents a non-void, static (Shared in Visual Basic) method that takes one argument, it is the implementing method for the node.

• 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 null.

Node Type and Lifted versus Non-Lifted

If the implementing method is not null:

• 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 null, the type of the node is expression.Type. If expression.Type is non-nullable, the node is not lifted. Otherwise, the node is lifted.

Negate(Expression)

Source:

UnaryExpression.cs

Creates a UnaryExpression that represents an arithmetic negation operation.

public:
 static System::Linq::Expressions::UnaryExpression ^ Negate(System::Linq::Expressions::Expression ^ expression);

public static System.Linq.Expressions.UnaryExpression Negate (System.Linq.Expressions.Expression expression);

static member Negate : System.Linq.Expressions.Expression -> System.Linq.Expressions.UnaryExpression

Public Shared Function Negate (expression As Expression) As UnaryExpression

Parameters

expression

Expression

An Expression to set the Operand property equal to.

Returns

UnaryExpression

A UnaryExpression that has the NodeType property equal to Negate and the Operand property set to the specified value.

Exceptions

ArgumentNullException

expression is null.

InvalidOperationException

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

Examples

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

// 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.
Console.WriteLine(Expression.Lambda<Func<int>>(negateExpr).Compile()());

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

' 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.
Console.WriteLine(Expression.Lambda(Of Func(Of Integer))(negateExpr).Compile()())

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

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 null.

Node Type and Lifted versus Non-Lifted

If the implementing method is not null:

• 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 null, the type of the node is expression.Type. If expression.Type is non-nullable, the node is not lifted. Otherwise, the node is lifted.