Difference between parameterless catch and other catch

Question

I have there piece of code

//Code 1                        Code 2                          Code 3
try                             try                             try
{                               {                               {
    //Exp occur                     //Exp occur                     //Exp occur 
}                               }                               }
catch (Exception e)             catch (Exception)               catch
{                               {                               {
    //Handle exp                    //Handle exp                    //Handle exp
}                               }                               }

What is the difference between all of three codes
P.S. I'm new to C# and as far as Java or Objective-C is concerned this syntax throws error

Answer 1

Code 1

Its catching Exception in an object e which can be later used for exception handling. For example you can log the Message property or view stack trace using e.Message or e.StackTrace

Code 2

You are catching all the exception of the base type Exception but since you don't have any object related to it, you can only throw that exception so that it can bubble up or you may ignore the exception. If in that code you had :

catch(InvalidCastException)

Then all the InvalidCastException will be handled in the block without the exception object

Code 3

You are catching all type of exceptions irrespective of their type, which is similar to your code 2 with base class Exception

try-catch - MSDN

Although the catch clause can be used without arguments to catch any type of exception, this usage is not recommended. In general, you should only catch those exceptions that you know how to recover from.

Its always better if you catch specific exceptions before catching the base one. Something like.

try
{
}
catch(InvalidCastException ex)
{
}
catch(Exception ex)
{
}

try - catch - MSDN

It is possible to use more than one specific catch clause in the same try-catch statement. In this case, the order of the catch clauses is important because the catch clauses are examined in order. Catch the more specific exceptions before the less specific ones. The compiler produces an error if you order your catch blocks so that a later block can never be reached.