ParameterExpression Classe

Definizione

public ref class ParameterExpression : System::Linq::Expressions::Expression

public ref class ParameterExpression sealed : System::Linq::Expressions::Expression

public class ParameterExpression : System.Linq.Expressions.Expression

public sealed class ParameterExpression : System.Linq.Expressions.Expression

type ParameterExpression = class
    inherit Expression

Public Class ParameterExpression
Inherits Expression

Public NotInheritable Class ParameterExpression
Inherits Expression

Ereditarietà

Object

Expression

ParameterExpression

Esempio

Nell'esempio seguente viene illustrato come creare un MethodCallExpression oggetto che stampa il valore di un ParameterExpression oggetto utilizzando il Parameter metodo .

// 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

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

' Creating a parameter for the expression tree.
Dim param As ParameterExpression = Expression.Parameter(GetType(Integer))

' Creating an expression for the method call and specifying its parameter.
Dim methodCall As MethodCallExpression = Expression.Call(
        GetType(Console).GetMethod("WriteLine", New Type() {GetType(Integer)}),
        param
    )

' Compiling and invoking the methodCall expression.
Expression.Lambda(Of Action(Of Integer))(
    methodCall,
    New ParameterExpression() {param}
).Compile()(10)
' This code example produces the following output:
'
' 10

Commenti

Usare il Parameter metodo factory per creare un oggetto ParameterExpression.

Il valore della NodeType proprietà di un ParameterExpression oggetto è Parameter.