Using catch without arguments

Question

What is the difference between:

catch
{
    MessageBox.Show("Error.");
}

and:

catch (Exception ex)
{
    MessageBox.Show("Error.");
    //we never use ex, so is it better to use catch without arguments?
}

Answer 1

As of .NET 2, if you don't tweak the configuration? Nothing.

Before then, or with some config tweak I can't remember precisely, there was the possibility of an exception being thrown from unmanaged code which didn't get converted into an Exception-compatible object.

Note that there's another option in between, where you specify the type but no variable:

catch (Exception)
{
   ...
}

Personally I'd be very wary of catching an exception without even logging it. It may be required if you're calling a boneheaded API, but it's generally best avoided.