Question

What are the pros and cons of implementing a custom exception as follows:
Create an enum which represents error messages in its descriptions:

public class Enums
{
    public enum Errors
    {
        [Description("This is a test exception")]
        TestError,
        ...
    }
}

Create a custom exception class:

public class CustomException : ApplicationException
{
    protected Enums.Errors _customError;
    public CustomException(Enums.Errors customError)
    {
        this._customError = customError;
    }
    public override string Message
    {
        get
        {
            return this._customError!= Enums.Errors.Base ? this.customError.GetDescription() : base.Message;
        }
    }  
}  

The GetDescription method is an enum extension method which gets the enum description using reflection. This way, I can throw exception like:

throw new customException(enums.Errors.TestError);  

And show it to the user in catch block like:

Console.WriteLn(ex.Message);  

I’ve seen this approach recommended by an MVP. What are the benefits of this approach over the followings:

• Using generic exception: throw new Exception(“Error Message”);.
• Using Custom Exception: Define custom exceptions for any situation. e.g. (WebServiceException class, AuthenticationException class, etc.)

Here’s the link to the recommendation by the MVP.

Thank you.

Answer 1

Personally, i don’t think it’s a good idea.

You should always throw as specific exceptions as possible. The same goes for catching.

It’s easy to decide if we want to catch a WebServiceException or AuthenticationException, but with your Enum-example, we have to parse a string to decide if we want to catch it or not. What happens if this message changes?

I don’t think it has any benefits at all. For each error type, you have to create a new Enum member. Why not create a new class instead?