Try Catch Finally

Question

Hi.

I was wondering if anybody could explain to me the purpose of the Finally block in exception handling. For example, what is the difference between these two pieces of code.

Example 1:

try
{
// open a file
}
catch (IOException ioe)
{
// log the error or something
}
finally
{
// do more stuff
}

Example 2:

try
{ // open a file
}
catch (IOException ioe)
{
// log the error or something
}
// do more stuff

Thanks,

Dave

arvind haritus · Answer

Hi David your code will be fine if try bolck execute only (means no exception there) if you have any exception then catch block is execute and after that execution is stop. In this situation your connection not close. so we use finally because of it execute in both condition (try catch).

David · Answer

Thank you for the response. I went in and added line breaks to my post (didn't know I had to do that manually) so maybe it will be more clear now. But I'll use your examples now. Sample 3 try { Connection.Open(); // Do something } catch(Exception exp) { } Connection.Close(); What would be the difference between that and your sample two? Dave

Mahesh Chand · Answer

Finally is very useful when you must execute some code no matter what happens. You don't need to use it unless you want to make sure some piece of code must be executed. For example if you are using Connection and you want to make sure by the end of the method connection must be close you put Connection.Close() method in finally. For example check these two psuedo code samples: Sample 1: try { Connection.Open(); // Do something Connection.Close(); } catch(Exception exp) { } Sample 2: try { Connection.Open(); // Do something } catch(Exception exp) { } Finally { Connection.Close(); } Now let's say there is an exception in code //Do Something in first sample connection will not be closed but in second sample connection will close because Finally block executes at very last.