Expression.Assign(Expression, Expression) Méthode

Définition

Espace de noms:
System.Linq.Expressions
Assemblys:
System.Core.dll, System.Linq.Expressions.dll
Assembly:
System.Core.dll
Assembly:
System.Linq.Expressions.dll
Assembly:
netstandard.dll

Crée un BinaryExpression qui représente une opération d’affectation.

public:
 static System::Linq::Expressions::BinaryExpression ^ Assign(System::Linq::Expressions::Expression ^ left, System::Linq::Expressions::Expression ^ right);
public static System.Linq.Expressions.BinaryExpression Assign(System.Linq.Expressions.Expression left, System.Linq.Expressions.Expression right);
static member Assign : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression -> System.Linq.Expressions.BinaryExpression
Public Shared Function Assign (left As Expression, right As Expression) As BinaryExpression

Paramètres

left
Expression

Pour Expression définir la Left propriété égale à.

right
Expression

Pour Expression définir la Right propriété égale à.

Retours

BinaryExpression

Qui BinaryExpression a la NodeType propriété égale à Assign et les LeftRight propriétés définies sur les valeurs spécifiées.

Exemples

L’exemple de code suivant montre comment créer une expression qui représente une opération d’affectation.

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

// To demonstrate the assignment operation, we create a variable.
ParameterExpression variableExpr = Expression.Variable(typeof(String), "sampleVar");

// This expression represents the assignment of a value
// to a variable expression.
// It copies a value for value types, and
// copies a reference for reference types.
Expression assignExpr = Expression.Assign(
    variableExpr,
    Expression.Constant("Hello World!")
    );

// The block expression allows for executing several expressions sequentually.
// In this block, we pass the variable expression as a parameter,
// and then assign this parameter a value in the assign expression.
Expression blockExpr = Expression.Block(
    new ParameterExpression[] { variableExpr },
    assignExpr
    );

// Print out the assign expression.
Console.WriteLine(assignExpr.ToString());

// The following statement first creates an expression tree,
// then compiles it, and then executes it.
Console.WriteLine(Expression.Lambda<Func<String>>(blockExpr).Compile()());

// This code example produces the following output:
//
// (sampleVar = "Hello World!")
// Hello World!

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

' To demonstrate the assignment operation, create a variable.
Dim variableExpr As ParameterExpression = Expression.Variable(GetType(String), "sampleVar")

' This expression represents the assignment of a value
' to a variable expression.
' It copies a value for value types, and it
' copies a reference for reference types.
Dim assignExpr As Expression = Expression.Assign(
    variableExpr,
    Expression.Constant("Hello World!")
    )

' The block expression allows for executing several expressions sequentually.
' In this block, you pass the variable expression as a parameter,
' and then assign this parameter a value in the assign expression.
Dim blockExpr As Expression = Expression.Block(
      New ParameterExpression() {variableExpr}, assignExpr
      )

' Print the assign expression.
Console.WriteLine(assignExpr.ToString())

' The following statement first creates an expression tree,
' then compiles it, and then executes it. 
Console.WriteLine(Expression.Lambda(Of Func(Of String))(blockExpr).Compile()())

' This code example produces the following output:
'
' (sampleVar = "Hello World!")
' Hello World!

Remarques

L’expression Assign copie une valeur pour les types valeur et copie une référence pour les types référence.

S’applique à