在ASP.NET中使用MySql：关闭连接是否真的释放表锁？

Question

I'm working on an ASP.NET application where, as part of some logic, I want to lock some tables and do work on them. The method runs in a separate thread running as a kind of background task, spawned via a Task. The problem comes in with the error handling...

The code looks more or less like this:

MySqlConnection connection = new MySqlConnection(ConfigurationManager.AppSettings["prDatabase"]);
try
{
    connection.Open();
    MySqlCommand lock_tables = new MySqlCommand(Queries.lockTables(), connection);
    lock_tables.ExecuteNonQuery();

    // do a bunch of work here

    MySqlCommand unlock_tables = new MySqlCommand(Queries.unlockTables(), connection);
    unlock_tables.ExecuteNonQuery();
}
catch (MySqlException mex)
{
    // Mostly error logging here
}
finally
{
    connection.Close();
}

Pretty simple stuff. Everything works fine and dandy assuming nothing goes wrong. That's a terrible assumption to make, though, so I deliberately set up a situation where things would foul up in the middle and move to the finally block.

The result was that my table locks remained until I closed the app, which I learned by trying to access the tables with a different client once the method completed. Needless to say this isn't my intention, especially since there's another app that's supposed to access those tables once I'm done with them.

I could quickly fix the problem by explicitly releasing the locks before closing the connection, but I'm still left curious about some things. Everything I've read before has sworn that closing a connection should implicitly release the table locks. Obviously in this case it isn't. Why is that? Does connection.Close() not actually completely close the connection? Is there a better way I should be closing my connections?

Answer 1

Try wrapping your Connection and MySqlCommand instance in a using statement. That will release the objects as soon as it leaves the brackets.

    using(MySqlConnection conn = new MySqlConnection(connStr))
{
   conn.Open();
   using(MySqlCommand command  = new MySqlCommand("command to execute",conn))
{
   //Code here..
}

}