Type.Missing Field
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Represents a missing value in the Type information. This field is read-only.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared ReadOnly Missing As Object
public static readonly Object Missing
Remarks
Use the Missing field for invocation through reflection to obtain the default value of a parameter. If the Missing field is passed in for a parameter value and there is no default value for that parameter, an ArgumentException is thrown.
Platform Notes
.png "Silverlight for Windows Phone"){kind=icon}
Silverlight for Windows Phone
The Type.Missing field does not throw ArgumentException when the called method has no default value for a parameter.
Examples
The following code example shows the use of the Missing field to invoke a method with its default arguments.
There is no C# example, because C# cannot declare optional parameters.
.gif "Note") Note: |
|---|
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control. |
Option Strict Off
Imports System.Reflection
Public Class OptionalArg
Public Function MyMethod(ByVal a As Integer, _
Optional ByVal b As Double = 1.2, Optional ByVal c As Integer = 1) As String
Return "a = " & a & " b = " & b & " c = " & c
End Function
End Class
Public Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim o As New OptionalArg()
Dim binding As BindingFlags = BindingFlags.Public Or BindingFlags.Instance Or _
BindingFlags.InvokeMethod Or BindingFlags.OptionalParamBinding
Dim t As Type = GetType(OptionalArg)
Dim param As Object() = {10, 20, 30}
Dim result As Object = _
t.InvokeMember("MyMethod", binding, Nothing, o, New Object() {10, 55.3, 12})
outputBlock.Text &= result & vbLf
result = _
t.InvokeMember("MyMethod", binding, Nothing, o, New Object() {10, 55.3, Type.Missing})
outputBlock.Text &= result & vbLf
result = _
t.InvokeMember("MyMethod", binding, Nothing, o, New Object() {10, Type.Missing, Type.Missing})
outputBlock.Text &= result & vbLf
End Sub
End Class
' This example produces the following output:
'
'a = 10 b = 55.3 c = 12
'a = 10 b = 55.3 c = 1
'a = 10 b = 1.2 c = 1
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.