Článek
11/18/2011

UnaryExpression Class

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

Represents an expression that has a unary operator.

Inheritance Hierarchy

System.Object
System.Linq.Expressions.Expression
System.Linq.Expressions.UnaryExpression

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

Syntax

'Declaration
Public NotInheritable Class UnaryExpression _
    Inherits Expression

public sealed class UnaryExpression : Expression

The UnaryExpression type exposes the following members.

Properties

	Name	Description
	CanReduce	Gets a value that indicates whether the expression tree node can be reduced. (Overrides Expression.CanReduce.)
	IsLifted	Gets a value that indicates whether the expression tree node represents a lifted call to an operator.
	IsLiftedToNull	Gets a value that indicates whether the expression tree node represents a lifted call to an operator whose return type is lifted to a nullable type.
	Method	Gets the implementing method for the unary operation.
	NodeType	Returns the node type of this Expression. (Overrides Expression.NodeType.) In Silverlight for Windows Phone Windows Phone OS 7.1, this member is inherited from Expression.NodeType. In XNA Framework Windows Phone OS 7.0, this member is inherited from Expression.NodeType.
	Operand	Gets the operand of the unary operation.
	Type	Gets the static type of the expression that this Expression represents. (Overrides Expression.Type.) In Silverlight for Windows Phone Windows Phone OS 7.1, this member is inherited from Expression.Type. In XNA Framework Windows Phone OS 7.0, this member is inherited from Expression.Type.

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Methods

	Name	Description
	Accept	Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Inherited from Expression.)
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Reduce	Reduces the expression node to a simpler expression. (Overrides Expression.Reduce().)
	ReduceAndCheck	Reduces this node to a simpler expression. If CanReduce returns true, this should return a valid expression. This method can return another node which itself must be reduced. (Inherited from Expression.)
	ReduceExtensions	Reduces the expression to a known node type (that is not an Extension node) or just returns the expression if it is already a known type. (Inherited from Expression.)
	ToString	Returns a textual representation of the Expression. (Inherited from Expression.)
	Update	Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
	VisitChildren	Reduces the node and then calls the visitor delegate on the reduced expression. The method throws an exception if the node is not reducible. (Inherited from Expression.)

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Remarks

The following table summarizes the factory methods that can be used to create a UnaryExpression that has a specific node type.

NodeType	Factory Method
ArrayLength	ArrayLength
Convert	Convert
ConvertChecked	ConvertChecked
Negate	Negate
NegateChecked	NegateChecked
Not	Not
Quote	Quote
TypeAs	TypeAs
UnaryPlus	UnaryPlus

In addition, the MakeUnary methods can also be used to create a UnaryExpression. These factory methods can be used to create a UnaryExpression of any node type that represents a unary operation. The parameter of these methods that is of type NodeType specifies the desired node type.

Examples

The following example creates a UnaryExpression object that represents the reference conversion of a non-nullable integer expression to the nullable integer type.

' Create a UnaryExpression that represents a reference
' conversion of an Integer to an Integer? (a nullable Integer).
Dim typeAsExpression As System.Linq.Expressions.UnaryExpression = _
    System.Linq.Expressions.Expression.TypeAs( _
        System.Linq.Expressions.Expression.Constant(34, Type.GetType("System.Int32")), _
        Type.GetType("System.Nullable`1[System.Int32]"))

outputBlock.Text &= typeAsExpression.ToString() & vbCrLf

' This code produces the following output:
'
' (34 As Nullable`1)

// Create a UnaryExpression that represents a
// conversion of an int to an int?.
System.Linq.Expressions.UnaryExpression typeAsExpression =
    System.Linq.Expressions.Expression.TypeAs(
        System.Linq.Expressions.Expression.Constant(34, typeof(int)),
        typeof(int?));

outputBlock.Text += typeAsExpression.ToString() + "\n";

// This code produces the following output:
//
// (34 As Nullable`1)

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.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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