Expression.TypeAs Method (System.Linq.Expressions)

TypeAs Method

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This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

Expression..::.TypeAs Method

Creates a UnaryExpression that represents an explicit reference or boxing conversion where nullNothingnullptra null reference (Nothing in Visual Basic) is supplied if the conversion fails.

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

Syntax

Visual Basic (Declaration)

Public Shared Function TypeAs ( _
    expression As Expression, _
    type As Type _
) As UnaryExpression

Visual Basic (Usage)

Dim expression As Expression
Dim type As Type
Dim returnValue As UnaryExpression

returnValue = Expression.TypeAs(expression, _
    type)

public static UnaryExpression TypeAs(
    Expression expression,
    Type type
)

Visual C++

public:
static UnaryExpression^ TypeAs(
    Expression^ expression, 
    Type^ type
)

JScript

public static function TypeAs(
    expression : Expression, 
    type : Type
) : UnaryExpression

Parameters

expression: Type: System.Linq.Expressions..::.Expression
An Expression to set the Operand property equal to.

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

Return Value

Type: System.Linq.Expressions..::.UnaryExpression
A UnaryExpression that has the NodeType property equal to TypeAs and the Operand and Type properties set to the specified values.

Exceptions

Exception	Condition
ArgumentNullException	expression or type is nullNothingnullptra null reference (Nothing in Visual Basic).

Remarks

The Method property of the resulting UnaryExpression is nullNothingnullptra null reference (Nothing in Visual Basic). The IsLifted and IsLiftedToNull properties are both false.

Examples

The following example demonstrates how to use the TypeAs(Expression, Type) method to create a UnaryExpression that represents the reference conversion of a non-nullable integer expression to the nullable integer type.

Visual Basic

' Create a UnaryExpression that represents a reference
' conversion of an Integer to an Integer? (a nullable Integer).
Dim typeAsExpression As System.Linq.Expressions.UnaryExpression = _
    System.Linq.Expressions.Expression.TypeAs( _
        System.Linq.Expressions.Expression.Constant(34, Type.GetType("System.Int32")), _
        Type.GetType("System.Nullable`1[System.Int32]"))

Console.WriteLine(typeAsExpression.ToString())

' This code produces the following output:
'
' (34 As Nullable`1)

// Create a UnaryExpression that represents a
// conversion of an int to an int?.
System.Linq.Expressions.UnaryExpression typeAsExpression =
    System.Linq.Expressions.Expression.TypeAs(
        System.Linq.Expressions.Expression.Constant(34, typeof(int)),
        typeof(int?));

Console.WriteLine(typeAsExpression.ToString());

// This code produces the following output:
//
// (34 As Nullable`1)

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5

Reference

Expression Class

Expression Members

System.Linq.Expressions Namespace