C# - Why implement standard exception constructors?

Question

From MSDN, code analysis warning CA1032:

 Exception types must implement the following constructors: 

• public NewException()
• public NewException(string)
• public NewException(string, Exception)
• protected or private NewException(SerializationInfo, StreamingContext)

I understand the purpose behind the serialization constructor, but is the rationale behind "requiring" the others? Why shouldn't I just define whatever constructors make sense for usage of my exception? What if I never want to throw MyException without passing in a message- why should I define a parameterless constructor? What if I want MyException to have an int property and I only want constructors that initialize that property?

Answer 1

This is a warning, not a requirement. It's basically principle of least surprise. Providing all 4 makes it easier for people used to "regular" C# exceptions to use yours. If you have a good reason to ignore the guideline, do so. But it will break certain usage scenarios, and make your class a little less intuitive.

Answer 2

You have gotten some good answers. I just want to add that providing these extra constructors does not necessarily require a lot of coding. Since they are already implemented in the base class, you can simply let that one do the work:

public class MyCustomException : Exception {     public MyCustomException() : base() { }     public MyCustomException(string message) : base(message) { }     public MyCustomException(string message, Exception innerException) : base(message, innerException) { }     // and so on... } 

So you will only need to implement code where the behaviour of your exception deviates from that of the base class.