Question

I have an ASP.NET website that uses mysql as it’s database. I notice there are a lot of connections “sleeping” when I show a full process list. Today we had some errors “The timeout period elapsed prior to obtaining a connection from the pool.”. If the processes are “sleeping” then are they still open from the code? All MySQL connections in the code are in using statements. Can I rely on the using statement to properly close connections?

Edit Code:
I am using this class to create my connection:

public class DbAccess
{
    public static MySqlConnection OpenConnection(string connectionStringName)
    {
        string connectionString = ConfigurationManager.ConnectionStrings[connectionStringName].ConnectionString;
        if (string.IsNullOrEmpty(connectionString))
        {
            throw new ArgumentException("Connection string " + connectionStringName + " does not exist.");
        }
        MySqlConnection connection = new MySqlConnection(connectionString);
        connection.Open();
        return connection;
    }
}

Then I am calling it like this:

using (MySqlConnection connection = DbAccess.OpenConnection(connectionString))
{
    //Code Here
}

Some additional info: Resetting MySql did not make the errors go away, but resetting my app pool did..

Answer 1

C# using blocks are guaranteed to call the .Dispose() method of the object, even if an exception is thrown. That means it’s safe, as long as your provider uses the .Dispose() method to close the connection. Looking in the documentation for that type, I see this excerpt (down in section 25.2.3.3.5):

From Open to Closed, using either the Close method or the Dispose method of the connection object.

This tells me you can close the connection via the Dispose method, and so a using block should be all you need.