Expression.Default(Type) Metode

Definisi

Ruang nama:

System.Linq.Expressions

Rakitan:

System.Linq.Expressions.dll

Sumber:

DefaultExpression.cs

Membuat yang DefaultExpression memiliki properti yang Type diatur ke jenis yang ditentukan.

public:
 static System::Linq::Expressions::DefaultExpression ^ Default(Type ^ type);

public static System.Linq.Expressions.DefaultExpression Default (Type type);

static member Default : Type -> System.Linq.Expressions.DefaultExpression

Public Shared Function Default (type As Type) As DefaultExpression

Parameter

type

Type

A Type untuk mengatur Type properti sama dengan.

Mengembalikan

DefaultExpression

DefaultExpression Properti yang memiliki NodeType properti sama dengan Default dan Type properti diatur ke jenis yang ditentukan.

Contoh

Contoh kode berikut menunjukkan cara membuat ekspresi yang mewakili nilai default untuk jenis tertentu.

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

// This expression represents the default value of a type
// (0 for integer, null for a string, etc.)
Expression defaultExpr = Expression.Default(
                            typeof(byte)
                        );

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

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

// This code example produces the following output:
//
// default(Byte)
// 0

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

' This expression represents the default value of a type
' (0 for integer, null for a string, and so on).
Dim defaultExpr As Expression = Expression.Default(
                                        GetType(Byte)
                                    )

' Print the expression.
Console.WriteLine(defaultExpr.ToString())

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

' This code example produces the following output:
'
' default(Byte)
' 0