Why is the Catch(Exception) almost always a bad Idea?

Question

Why is the Catch(Exception) almost always a bad Idea?

Answer 1

Because when you catch exception you're supposed to handle it properly. And you cannot expect to handle all kind of exceptions in your code. Also when you catch all exceptions, you may get an exception that cannot deal with and prevent code that is upper in the stack to handle it properly.

The general principal is to catch the most specific type you can.

Answer 2

Because you don't really know why an exception happened, and several exceptions require very special car to be handled correctly (if possible at all), such as a OutOfMemoryException and similar low-level system exceptions.

Therefore, you should only catch exceptions:

• which you know exactly how to deal with it (e.g. FileNotFoundException or so)
• when you will re-raise them afterwards (for instance to perform post-fail cleanup)
• when you need to transport the exception to another thread

Answer 3

It depends on what you need. If you need to handle different types of exceptions in different ways then you should use multiple catch blocks and catch as much specific exceptions as you can.

But sometimes you may need to handle all exceptions in the same way. In such cases catch(Exception) may be ok. For example:

    try
    {
        DoSomething();
    }
    catch (Exception e)
    {
        LogError(e);
        ShowErrorMessage(e); // Show "unexpected error ocurred" error message for user.
    }

Answer 4

You should only catch exceptions if you can properly handle them. As you cannot properly handle all possible exceptions you should not catch them :-)

Answer 5

Short story: it's called bug masking. If you have a piece of code which is not working well and throwing exceptions (or you pass malformed input to that piece of code) and you just blind your eyes by catching all possible exceptions, you will actually never uncover the bug and fix it.

Answer 6

almost because this can be useful when used with throw;

try
{
    //database work
    tx.commit();
}
catch(Exception)
{
    tx.rollback();
    throw;
}