Expression.Assign(Expression, Expression) Metoda

Definicja

Przestrzeń nazw:

System.Linq.Expressions

Zestaw:

System.Linq.Expressions.dll

Source:

BinaryExpression.cs

Tworzy obiekt BinaryExpression reprezentujący operację przypisania.

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

Parametry

left

Expression

Element , Expression aby ustawić właściwość równą Left .

right

Expression

Element , Expression aby ustawić właściwość równą Right .

Zwraca

BinaryExpression

WłaściwośćBinaryExpression, która ma właściwość równą AssignNodeType i Left właściwości i Right ustawioną na określone wartości.

Przykłady

W poniższym przykładzie kodu pokazano, jak utworzyć wyrażenie reprezentujące operację przypisania.

// 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!

Uwagi

Wyrażenie Assign kopiuje wartość dla typów wartości i kopiuje odwołanie do typów referencyjnych.