Статья
11/17/2011

Expression.Default Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Creates a DefaultExpression that has the Type property set to the specified type.

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

Syntax

'Declaration
Public Shared Function Default ( _
    type As Type _
) As DefaultExpression

public static DefaultExpression Default(
    Type type
)

Parameters

type
Type: System.Type
A Type to set the Type property equal to.

Return Value

Type: System.Linq.Expressions.DefaultExpression
A DefaultExpression that has the NodeType property equal to Default and the Type property set to the specified type.

Examples

The following code example shows how to create an expression that represents a default vaule for a given type.

' 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.
outputBlock.Text &= defaultExpr.ToString() & vbCrLf

' The following statement first creates an expression tree,
' then compiles it, and then executes it.
outputBlock.Text &=
    Expression.Lambda(Of Func(Of Byte))(defaultExpr).Compile()() & vbCrLf

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

// 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.
outputBlock.Text += defaultExpr.ToString() + "\n";

// The following statement first creates an expression tree,
// then compiles it, and then executes it.
outputBlock.Text +=
    Expression.Lambda<Func<byte>>(defaultExpr).Compile()() + "\n";

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

Version Information

Silverlight

Supported in: 5, 4

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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