Mysql database freezes with Visual Sudio C#.

Question

I a'm reading values from raspberry pi mysql database with visual studio c#
If the database is not available and I am trying to read from it, the c# app
freezes for about 15 seconds.

Is it possible to make it not to freeze when checking if the database is available?

Here is the code

 string connString = "SERVER='192.168.86.41';DATABASE='spaceinformation';UID='******';PASSWORD='******'";  
 private void FormMeasurement_Load(object sender, EventArgs e)  
        {  
            try  
            {  
                using (var connection = new MySqlConnection(connString))  
                {  
                    connection.Open();  
  
                    query = "select * from weather";  
                    using (var command = new MySqlCommand(query, connection))  
                    {  
                        using (var reader = command.ExecuteReader())  
                        {  
                            while (reader.Read())  
                            {  
                                listBoxMeasurement.Items.Add(string.Format("Temperature: {0}   Humidity: {1}   Date: {2}", reader.GetString("temp"), reader.GetString("hum"), reader.GetString("datecreated")));  
                            }  
                        }  
                    }  
                    connection.Close();  
                }  
            }  
            catch  
            {  
                MessageBox.Show("Database is not available for moment!");  
                listBoxMeasurement.Enabled = false;  
            }  
        }  

Answer 1

I believe this is because the MySqlConnection.Open is a blocking IO operation & it's waiting for the default timeout to elapse before reaching your catch block.

There is an OpenAsync method that is the asynchronous non-blocking version of this method, but unfortunately the MySql driver for C# hasn't actually implemented it, so it just falls back to the Open implementation. It states that in their docs too:
https://dev.mysql.com/doc/dev/connector-net/6.10/html/Methods_T_MySql_Data_MySqlClient_MySqlConnection.htm

   The cancellation token can optionally be honored.The default implementation invokes the synchronous Open() call and returns a completed task  

You can work around that by running your MySql block inside a new Task, which won't prevent your FormMeasurement_Load from finishing. You can do that like this:

   _ = Task.Run(async () => {  
       ...  
   });  

The code inside that callback would be your existing code.

EDIT:
You'll also just need to replace this:

   listBoxMeasurement.Items.Add(string.Format("Temperature: {0}   Humidity: {1}   Date: {2}", reader.GetString("temp"), reader.GetString("hum"), reader.GetString("datecreated")));  

For this:

   listBoxMeasurement.BeginInvoke(() => {  
       listBoxMeasurement.Items.Add(string.Format("Temperature: {0}   Humidity: {1}   Date: {2}", reader.GetString("temp"), reader.GetString("hum"), reader.GetString("datecreated")));  
   });  

And this:

   listBoxMeasurement.Enabled = false;  

For this:

   listBoxMeasurement.BeginInvoke(() => {  
       listBoxMeasurement.Enabled = false;  
   });  

Answer 2

may be your problem will be solved after writing a parameter.