C# Using SQL Method needs a close-method?

Question

When using a using block for SQL connections in C#, does this also a close method? I'm asking as I need to explicitly use the con.Open() method. I found this example:

using (SqlConnection con = new SqlConnection(connectionString))
{
   con.Open(); // open method

   string queryString = "select * from db";
   SqlCommand cmd = new SqlCommand(queryString, con);
   SqlDataReader reader = cmd.ExecuteReader();
   reader.Read();

   ???         // What about a close method?
}

Or does the using block close the connection itself?

using will call Dispose of connection and Dispose will call Close. — Daniil, Mar 25 '13 at 10:05
so when Im using it, using will close all connetions. All connections means global, or only this connections in this method/class where it is? — mnlfischer, Mar 25 '13 at 10:08
@ManuelFischer only connection in statement using(SqlConnection iWillDisposeConn = new... — Daniil, Mar 25 '13 at 10:11
You should really have your command and reader in `using` blocks also - they're disposable too. — Damien_The_Unbeliever, Mar 25 '13 at 10:15

score 0 · Answer 1 · answered Mar 25 '13 at 10:07

You don't have to close it - using is enough. MSDN says:

To ensure that connections are always closed, open the connection inside of a using block, as shown in the following code fragment. Doing so ensures that the connection is automatically closed when the code exits the block.

score 0 · Accepted Answer · answered Mar 25 '13 at 10:07

using translates to:

SqlConnection con = new SqlConnection(connectionString)
try
{
   con.Open(); <-- open method

   string queryString = "select * from db";
   SqlCommand cmd = new SqlCommand(queryString, con);
   SqlDataReader reader = cmd.ExecuteReader();
   reader.Read();
}
finally
{
    if (con!= null)
        ((IDisposable)con).Dispose();
}

where ((IDisposable)con.Dispose(); closes what is to be closed.

score 0 · Answer 3 · answered Mar 25 '13 at 10:08

0

No, you don't have to call the Close-Method of the SqlConnection. When it gets disposed on the end of the using, it closes automatically. (The Dispose-Method calls Close()) [1]

answered Mar 25 '13 at 10:08

jAC

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score 0 · Answer 4 · answered Mar 25 '13 at 10:09

0

The other answers are correct, however, I want to be a bit more explicit.
The MSDN states the following:

Close and Dispose are functionally equivalent.

Because using using will call Dispose a separate call to Close is not needed.

answered Mar 25 '13 at 10:09

Daniel Hilgarth

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score 0 · Answer 5 · answered Mar 25 '13 at 10:18

when you use the 'using' keyword and create a connection in it . the connection is open as far as there is the scope of the 'using' keyword when closing bracket is reached the connection is closed automatically as it was defined within a scope and the scope is not in exist

in other words treat it as the local variable which can be accessed within the scope only. hope this will help.

C# Using SQL Method needs a close-method?

5 Answers5