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Support Remote Clients with a Custom Exception Object

The custom Exception class I described in a column earlier this month will work fine … as long as the .NET Framework doesn't need to serialize your Exception object to return it to a remote client. If you want to make the extra effort, you can add serialization support to your custom Exception class.

To support serialization you first need to decorate your Exception class with the Serializable attribute. And, if you haven't added any custom properties to your Exception class, that's all you need to do.

But if you do have custom properties on your Exception class then during serialization you must do two things. First, you must override the base Exception object's GetObjectData method. In that method you should call the base version of the method to ensure that the default serialization is performed.

After that, you need to add the values of any custom properties to the SerializationInfo parameter passed to the method, saving the parameters under some name you make up. Here's a version of the method that adds a value called BadOption from a variable in the class to the serialized version of the object:

Private _Option As String
Public Overrides Sub GetObjectData(info As SerializationInfo, 
                                   context As StreamingContext)
  MyBase.GetObjectData(info, context)

  If info IsNot Nothing Then
    info.AddValue("BadOption", Me._option)
  End If

End Sub

You also need to add a constructor that the .NET Framework will call during the deserialization process. In that constructor you need to extract your value from the SerializationInfo, using the name you saved the value under. Once you've retrieved the value you can then update your customer property with it. This example retrieves and updates my BadOption value:

Protected Sub New(SerializationInfo As SerializationInfo,
                  StreamingContext As StreamingContext)
  MyBase.New(SerializationInfo, StreamingContext)

  If SerializationInfo IsNot Nothing Then
    Me._option = SerializationInfo.GetString("BadOption")
  End If

End Sub

Let me know how helpful this is in the comment section, or send me e-mail!

Posted by Peter Vogel on 02/06/2015 at 2:20 PM


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