Auto Connect SqlConnection

Question

Every time I had problem with my SQL Server connection (ex. someone switch of server) my application will show an exception message in a messagebox. I don't know when will the connection available except I keep trying to open the connection / execute a query.

So I create a wait form that will appear if connection is unavailable, keep trying to open the connection, and close itself when connection is available again.

To hide the freeze from user, I use a background worker.

This is the background worker code

    private void StartLoader(object sender, DoWorkEventArgs e)
    {
        for (int i = 1; i <= 10; i++)
        {
            if (this.par.sqSuccess) //if no error, means connection is available, stop looping
            {
                break;
            }
            else
            {
                i -= 1;
            }

            System.Threading.Thread.Sleep(5000); //report progress every 5 second
        }

This is the background worker's progress changed event

this.cnn = new SqlConnection(this.par.Constr);

try
{
   this.cnn.Open(); //SqlConnection

   this.par.sqSuccess = true; //if no error, then I change this variable
}
catch (Exception ex)
{
   this.par.Exception = ex.Message;
}
finally
{
   if (this.cnn != null) { this.cnn.Dispose(); }
}
if (this.par.sqSuccess) { this.Close(); }

After everything is complete, I tried to stop SQL Server service from services.msc, then I try to connect.

The wait form will appear and keep doing its job.

A few second after I try to connect, I start the service again and the wait form did close, success. This is the problem, when I wait a little bit longer before I start the service again, the wait form still closed, but it takes a while.

After I check everything, it seems like the cnn.open() queue up and the longer I stop the service, the longer it takes for the wait form to close.

I searched google and try to add Connect Timeout=3; behind my connection string, as I'm sure my thread.sleep(5000) won't make them queue up, but still not working.

Someone told me to use cnn.OpenAsync();

After reading the documentation about OpenAsync, this is what I do.

    static async Task<ConnectionState> Method(SqlConnection cnn)
    {
        await cnn.OpenAsync();
        return cnn.State;
    }

And this

    private void SQLClientLoader_Load(object sender, EventArgs e)
    {
        do
        {
            this.cnn = new SqlConnection(this.par.Constr);

            try
            {
                ConnectionState cst = Method(cnn).Result;

                if (cst == ConnectionState.Open)
                {
                    this.par.sqSuccess = true;
                }
                else
                {

                }
            }
            catch (Exception ex)
            {
                this.par.sqSuccess = false;

                this.par.Exception = ex.Message;
            }
            finally
            {

            }
        } while ((bool)this.par.sqSuccess != true);
    }

The code above freezes my application every time the form load code executed.

I need simple instruction of how to wait for the cnn.Open process to finish or to cancel it if it takes too long.

Thank you in advance

Answer 1

You can set the ConnectionTimeout property for your SqlConnection in your code or in your ConnectionString. No need to use Async IMHO..

cnn.ConnectionTimeout = 5000

So this will create about a 10-second delay if connection does not work (connectiontimeout + Sleep(5000).