try/catch and using statements

Question

The following 2 sets of codes produce same results, but I'm wondering which of these is the correct way of wrapping with the try...catch block. What's the difference between the 2 of them?

Edited: Which of this will properly capture the error, and also to make sure the connection will be closed even if there is an exception.

1

try
{
    using (SqlConnection conn = new SqlConnection(connString))
    {
        SqlCommand cmd = new SqlCommand("Drop Table sometable", conn);
        cmd.Connection.Open();
        cmd.ExecuteNonQuery();
    }
}
catch
{
    //
}

2

using (SqlConnection conn = new SqlConnection(connString))
{
    try
    {
        SqlCommand cmd = new SqlCommand("Drop Table sometable", conn);
        cmd.Connection.Open();
        cmd.ExecuteNonQuery();
    }
    catch
    {
        //
    }
}

Both are fine, just be sure to close the connection inside the catch when you're using the 2nd example. — Steven Borges, May 01 '14 at 14:59
Correct as in which of this will properly capture the error, and also to make sure the connection will be closed even if there is an exception. — C.J., May 01 '14 at 15:00
@StevenBorges, why you think that connection will still open in 2-nd snippet? — Hamlet Hakobyan, May 01 '14 at 15:01

score 3 · Answer 1 · answered May 01 '14 at 15:02

3

The difference is that in the #2 SqlConnection conn object will be disposed after the catch block will be finished. In #1 your connection will be disposed and than you will end up in the catch block.

answered May 01 '14 at 15:02

milagvoniduak

3,214
1
18
18

score 2 · Answer 2 · answered May 01 '14 at 15:03

2

Both are fine, depended on if you want to catch an error when opening the connection, and then of course you need to close the connection when you are done with it. usually closing earlier is better.

answered May 01 '14 at 15:03

Mothware

312
2
10

score 1 · Answer 3 · answered May 01 '14 at 15:02

the difference is:

if you use code 2, and your connString you use in your using statement is invalid, it will throw an exception, because it is not in the try catch block.

in code 1, it will just catch that exception. but you will not be able to use your SqlConnection in the catch block

score 1 · Answer 4 · answered May 01 '14 at 15:33

I thik that you are aware of exception handling. We write all of our codes inside the catch block that can arise suspicious/unknown behavior to our applications. In that case the catch block handles the suspicious behavior of our application. In context to your above two block of codes .... For the first one- any exception caused by any one statement of your codes will be handled by catch block. But for second one- exception caused by "using (SqlConnection conn = new SqlConnection(connString))" statement cannot be handled by your catch block, because it is outside of the try block. To test this just place some false connection string in sqlconnection.

Hope this will gives you better understanding for your scenario.

score 0 · Answer 5 · answered May 01 '14 at 15:41

The using statement is a syntactic shortcut to represent a try/catch/finally. You could right your code as below, and would have the same effect as your examples above.

        SqlConnection conn
        try
        {
            conn = new SqlConnection(connString)
            SqlCommand cmd = new SqlCommand("Drop Table sometable", conn);
            cmd.Connection.Open();
            cmd.ExecuteNonQuery();
        }
        catch
        {
            //
        }
        finally
        {
           if(conn != null)
           {
                conn.Dispose()
           }
       }

try/catch and using statements

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5 Answers5