Missing Class
Represents a missing Object. This class cannot be inherited.
Assembly: mscorlib (in mscorlib.dll)
The following example shows how to use Missing to invoke a method with a default argument. To compile and run this code example, you must first compile the following Visual Basic code as a DLL assembly named Target.dll. Save the code as Target.vb. From the command line, use vbc /t:library Target.vb to compile the assembly.
Imports System
Public Class MissingSample
Public Shared Sub MyMethod(Optional k As Integer = 33)
Console.WriteLine("k = " & k.ToString())
End Sub
End Class
If you compile Target.dll in Visual Studio, by default the project name is used as the name of a namespace that contains the MissingSample class. Either remove the namespace from the Target project, or add a using Target; statement to the C# code (Imports Target in Visual Basic, using namespace Target; in Visual C++).
Note: |
|---|
Visual Basic code is used for Target.dll because C# and Visual C++ do not support optional parameters in managed code. Optional parameters are not part of the Common Language Specification. Therefore, code that uses optional parameters is not CLS-compliant. For more information, see Writing CLS-Compliant Code. |
When you compile the Visual Basic and C# versions of this code example, add references to Target.dll. For example, if you are compiling from the command line, use the /r:Target.dll option. The Visual C++ version of the code example already includes a #using statement for Target.dll.
Imports System Imports System.Reflection Public Module Example Sub Main() ' To invoke MyMethod with the default argument value, pass ' Missing.Value for the optional parameter. First, get the ' method. Dim mi As MethodInfo = _ GetType(MissingSample).GetMethod("MyMethod") ' Second, create an array of parameters to pass to the method. ' In this case, the array contains just one element. Dim arguments() As Object = { Missing.Value } ' Finally, invoke the method. Specify Nothing for the target ' object, because the method is Shared. mi.Invoke(Nothing, arguments) End Sub End Module ' This code example produces the following output: ' 'k = 33
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
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.
Note: