Error Handling in c#

It very much depends on what is happening in those function, where you want to handle the errors, and if you just want to log the error and move on to the next row/transaction/whatever. If you don't handle an error in (say) P4 then the error will be thrown up to the calling function, if you don't handle it there it will go up to the function calling that one and so on.

There are some articles on best practices for error handling on the following links

http://msdn.microsoft.com/en-us/library/seyhszts(v=vs.110).aspx[^]
Exception Handling Best Practices in .NET[^]
http://codebuild.blogspot.co.uk/2012/01/15-best-practices-about-exception.html[^]

[EDIT] Just had another thought. We often see code in QA here along the lines of

try
{
    P1();
}
catch (Exception)
{
    //do nothing
}

This is worse than not having any error handling as the exception is just "swallowed" and you will never know whether your program worked. Don't do this

If you don't do any error handling, any error which occurs in P2(), P3() or P4() would be propagated to the caller in the stack. Thus, in case of any error if you just want to exit, you don't have to do any thing extra in this example.

However, I would suggest to add some sort of logging or other exception handling in the main method (assuming P1 in this case) so that it can give you details later while debugging or trouble shooting.

Thus:

private void P1()
{
    try
    {
        P2();
        P3();
    }
    catch(Exception exception)
    {
        //Log or handle this exception
    }
}

private void P3()
{
    P4();
}

private void P4()
{
}