TRY-CATCH relative to USING

Question

I've been implementing TRY-CATCH relative to USING like the following example:

private void someDatabaseMethod(string userName) {

    try {

        using(var conn = new SqlConnection(connString))
        using(var comm = new SqlCommand()) {
            comm.Connection = conn;
            comm.CommandType = CommandType.Text;
            comm.CommandText = string.Concat(@"SELECT UserID FROM xxx WHERE UserName = '", userName,@"'");
            conn.Open();
            object x = comm.ExecuteScalar();
            UserID = (x==null)? 0: (int)x;
        }
    } catch(Exception) {
        throw;
    }
}

I've just seen this MSDN EXAMPLE which seems to point towards the TRY-CATCH being within the USING. So my example would look like the following:

private void someDatabaseMethod(string userName) {

        using(var conn = new SqlConnection(connString))
        using(var comm = new SqlCommand()) {
            comm.Connection = conn;
            comm.CommandType = CommandType.Text;
            comm.CommandText = string.Concat(@"SELECT UserID FROM xxx WHERE UserName = '", userName,@"'");

            try {

               conn.Open();
               object x = comm.ExecuteScalar();
               UserID = (x==null)? 0: (int)x;

            } catch(Exception) {
               throw;
            }
        }
}

Is this a more efficient layout? If so, why?

EXTRA ADDITIONAL NOTE

The reason for the TRY-CATCH is to re-throw the exception so that I bubble it up to the next level - so I'd like to have a CATCH somewhere in the code.

score 3 · Answer 1 · answered Apr 11 '13 at 09:10

3

It depends on your goals. If you want to do something with command or connection in catch block, then it should be within using.

answered Apr 11 '13 at 09:10

alex

12,464
3
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+1 for the classic "it depends" – whytheq Apr 11 '13 at 15:34

score 2 · Answer 2 · answered Apr 11 '13 at 09:11

2

If you just throw the catched exception, the try-catch block isn't necessary at all. The using will dispose the conenction and command properly.

answered Apr 11 '13 at 09:11

laszlokiss88

4,001
3
20
26

The reason for the `TRY-CATCH` is to re-throw the exception so that I can bubble it up to the next level - so I'd like to have a `CATCH` somewhere in the code. – whytheq Apr 11 '13 at 14:47

score 2 · Accepted Answer · answered Apr 11 '13 at 09:16

TRY-CATCH I use in using only if I want to LOG Exception or it I have transaction - to rollback it in except block. using is translated by compiler in TRY-FINALLY - you can check it with IL Disassembler (ildasm.exe) or reflector to release your disposable resources. so that using is equivalent to :

try 
{
 //do job
} 
finally
{
  Resource.Dispose()
}

score 2 · Answer 4 · answered Apr 11 '13 at 09:20

2

Second one is more efficient. For first one; you can not access connection object from catch block, and can not close it. Also if you was using a transaction over this connection, you could not rollback the transaction when any error occurs...

answered Apr 11 '13 at 09:20

Kenan Kocaerkek

319
3
9

+1 for first one - if it errors on `conn.Open();` what happens first: will the using deal with the problem and free resources ? or will it go to CATCH before using has a chance to garbage collect? – whytheq Apr 11 '13 at 14:50

score 0 · Answer 5 · edited May 23 '17 at 11:49

0

Don't catch exceptions you cannot handle at this place.
catch{throw;} is of no use except adding complexity
catch and handle exceptions as near at the exception source as you are able to handle them

Read extensive discussion here

edited May 23 '17 at 11:49

Community

1
1

answered Apr 11 '13 at 09:18

1

catch{throw;} bubbles the exception up to a higher level and it is dealt with there – whytheq Apr 11 '13 at 14:48
1

And therefore catch-throw is for nothing as the exception will "bubble" up also without this construct. – Apr 11 '13 at 15:51

TRY-CATCH relative to USING

5 Answers5