项目
11/18/2011

MissingMemberException Class

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The exception that is thrown when there is an attempt to dynamically access a class member that does not exist.

Inheritance Hierarchy

System.Object
  System.Exception
    System.SystemException
      System.MemberAccessException
        System.MissingMemberException
          System.MissingFieldException
          System.MissingMethodException

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Class MissingMemberException _
    Inherits MemberAccessException

[ComVisibleAttribute(true)]
public class MissingMemberException : MemberAccessException

The MissingMemberException type exposes the following members.

Constructors

	Name	Description
	MissingMemberException()	Initializes a new instance of the MissingMemberException class.
	MissingMemberException(String)	Initializes a new instance of the MissingMemberException class with a specified error message.
	MissingMemberException(String, Exception)	Initializes a new instance of the MissingMemberException class with a specified error message and a reference to the inner exception that is the root cause of this exception.

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Properties

	Name	Description
	Data	Gets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception.)
	HResult	Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception.)
	InnerException	Gets the Exception instance that caused the current exception. (Inherited from Exception.)
	Message	Gets the text string showing the class name, the member name, and the signature of the missing member. (Overrides Exception.Message.)
	StackTrace	Gets a string representation of the frames on the call stack at the time the current exception was thrown. (Inherited from Exception.)

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Methods

	Name	Description
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetBaseException	When overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the runtime type of the current instance. (Inherited from Exception.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Creates and returns a string representation of the current exception. (Inherited from Exception.)

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Remarks

Normally a compilation error is generated if the code attempts to access a nonexistent member of a class. MissingMemberException is designed to handle cases where a field or a method is deleted or renamed in one assembly and the change is not reflected in a second assembly. At runtime, MissingMemberException will be thrown when the code in the second assembly attempts to access the missing member in the first assembly.

MissingMemberException is the base class for MissingFieldException and MissingMethodException. In general it is better to use one of the derived classes of MissingMemberException to more precisely indicate the exact nature of the error. Throw a MissingMemberException if you are only interested in capturing the general case of a missing member error.

For a list of initial property values for an instance of MissingMemberException, see the MissingMemberException constructors.

Examples

This example shows what happens if you attempt to use reflection to call a method that does not exist and access a field that does not exist. The application recovers by catching the MissingMethodException, MissingFieldException, and MissingMemberException.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Reflection

Public Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Try
         ' Attempt to call a static DoSomething method defined in the Example class.
         ' However, because the Example class does not define this field, 
         ' a MissingFieldException is thrown.
         GetType(Example).InvokeMember("DoSomething", BindingFlags.Static Or BindingFlags.InvokeMethod, _
                                    Nothing, Nothing, Nothing)
      Catch e As MissingMethodException
         ' Show the user that the DoSomething method cannot be called.
         outputBlock.Text += String.Format("Unable to call the DoSomething method: {0}", e.Message) & vbCrLf
      End Try
      Try
         ' Attempt to access a static AField field defined in the Example class.
         ' However, because the Example class does not define this field, 
         ' a MissingFieldException is thrown.
         GetType(Example).InvokeMember("AField", BindingFlags.Static Or BindingFlags.SetField, _
                                    Nothing, Nothing, New [Object]() {5})
      Catch e As MissingFieldException
         ' Show the user that the AField field cannot be accessed.
         outputBlock.Text += String.Format("Unable to access the AField field: {0}", e.Message) & vbCrLf
      End Try
      Try
         ' Attempt to access a static AnotherField field defined in the Example class.
         ' However, because the Example class does not define this field, 
         ' a MissingFieldException is thrown.
         GetType(Example).InvokeMember("AnotherField", BindingFlags.Static Or BindingFlags.GetField, _
                                    Nothing, Nothing, Nothing)
      Catch e As MissingMemberException
         ' Notice that this code is catching MissingMemberException which is the  
         ' base class of MissingMethodException and MissingFieldException.
         ' Show the user that the AnotherField field cannot be accessed.
         outputBlock.Text += String.Format("Unable to access the AnotherField field: {0}", e.Message) & vbCrLf
      End Try
   End Sub
End Class
' This code example produces the following output:
'
' Unable to call the DoSomething method: Method 'App.DoSomething' not found.
' Unable to access the AField field: Field 'App.AField' not found.
' Unable to access the AnotherField field: Field 'App.AnotherField' not found.

using System;
using System.Reflection;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      try
      {
         // Attempt to call a static DoSomething method defined in the Example class.
         // However, because the Example class does not define this field, 
         // a MissingFieldException is thrown.
         typeof(Example).InvokeMember("DoSomething", BindingFlags.Static |
             BindingFlags.InvokeMethod, null, null, null);
      }
      catch (MissingMethodException e)
      {
         // Show the user that the DoSomething method cannot be called.
         outputBlock.Text += String.Format("Unable to call the DoSomething method: {0}", e.Message) + "\n";
      }

      try
      {
         // Attempt to access a static AField field defined in the Example class.
         // However, because the Example class does not define this field, 
         // a MissingFieldException is thrown.
         typeof(Example).InvokeMember("AField", BindingFlags.Static | BindingFlags.SetField,
             null, null, new Object[] { 5 });
      }
      catch (MissingFieldException e)
      {
         // Show the user that the AField field cannot be accessed.
         outputBlock.Text += String.Format("Unable to access the AField field: {0}", e.Message) + "\n";
      }

      try
      {
         // Attempt to access a static AnotherField field defined in the Example class.
         // However, because the Example class does not define this field, 
         // a MissingFieldException is thrown.
         typeof(Example).InvokeMember("AnotherField", BindingFlags.Static |
             BindingFlags.GetField, null, null, null);
      }
      catch (MissingMemberException e)
      {
         // Notice that this code is catching MissingMemberException which is the  
         // base class of MissingMethodException and MissingFieldException.
         // Show the user that the AnotherField field cannot be accessed.
         outputBlock.Text += String.Format("Unable to access the AnotherField field: {0}", e.Message) + "\n";
      }
   }
}
// This code example produces the following output:
//
// Unable to call the DoSomething method: Method 'App.DoSomething' not found.
// Unable to access the AField field: Field 'App.AField' not found.
// Unable to access the AnotherField field: Field 'App.AnotherField' not found.

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.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.