Dominique LeBlond: what happened in base class instructor

Question

public class MyException : Exception { public MyException ( string message ) : base ( message ) { } } try { if(len>5) throw new MyException(length cannot be > 5); } catch (MyException my) { Console.WriteLine(my.Message); } //----------------------------------- above length cannot be > 5 passed as parameter to base class constructor. What happened in base class instructor? How /why length cannot be > 5 passed to catch block?

amit_gupta14 · Answer

public class MyException : Exception { } try { if(len>5) throw new MyException(); } catch (MyException my) { Console.WriteLine(my.Message); } 1. In the above code we are not mentioning any derive class constructor will it use base class constructor? 2. If yes it means it will use Message property and that will be empty 3. Because Message property has no value then why the output is:Exception of type MyException was thrown.

denkai · Answer

wow a post with my name in it... When you derive from a class you inherit all public/protected members from the base class. The Exception class has a property called Message. When you call the base class constructor from your MyException class the base class initializes this property with the string you passed in. It looks something like this: public class Exception { private string _message; public Exception(string message) { _message = message; } public string Message { get { return _message; } } } Then when you call the message property from your MyException class you end up calling the property get from the base class and thus get the value specified in the constructor back. Keep in mind Message is only one of the properties you inherit. If you look at the your MyException class in an object browser (or with intellisense) you will see some more properties. This is what inheritance is all about I must also strongly suggest you read a little about it if you are finding yourself lost. cheers

bilnaad · Answer

maybe it's better to read some arcticles about inheritence. Then you will understand why it happens