ParameterExpression Class

Represents a named parameter expression.

System.Object
  System.Linq.Expressions.Expression
    System.Linq.Expressions.ParameterExpression

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

public class ParameterExpression : Expression

The ParameterExpression type exposes the following members.

  NameDescription
Public propertyCanReduceIndicates that the node can be reduced to a simpler node. If this returns true, Reduce() can be called to produce the reduced form. (Inherited from Expression.)
Public propertyIsByRefIndicates that this ParameterExpression is to be treated as a ByRef parameter.
Public propertySupported by Portable Class LibraryNameGets the name of the parameter or variable.
Public propertyNodeTypeReturns the node type of this Expression. (Overrides Expression.NodeType.)
Public propertyTypeGets the static type of the expression that this Expression represents. (Overrides Expression.Type.)
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  NameDescription
Protected methodAcceptDispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Overrides Expression.Accept(ExpressionVisitor).)
Public methodSupported by Portable Class LibraryEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Portable Class LibraryFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Portable Class LibraryMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodReduceReduces 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.)
Public methodReduceAndCheckReduces 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.)
Public methodReduceExtensionsReduces 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.)
Public methodSupported by Portable Class LibraryToStringReturns a textual representation of the Expression. (Inherited from Expression.)
Protected methodVisitChildrenReduces 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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Use the Parameter factory method to create a ParameterExpression.

The value of the NodeType property of a ParameterExpression object is Parameter.

The following example demonstrates how to create a MethodCallExpression object that prints the value of a ParameterExpression object by using the Parameter method.


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

// Creating a parameter for the expression tree.
ParameterExpression param = Expression.Parameter(typeof(int));

// Creating an expression for the method call and specifying its parameter.
MethodCallExpression methodCall = Expression.Call(
    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(int) }),
    param
);

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action<int>>(
    methodCall,
    new ParameterExpression[] { param }
).Compile()(10);

// This code example produces the following output:
//
// 10


.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.

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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