Error : "Fill: SelectCommand.Connection property has not been initialized."

Change the line

MySqlCommand cmd = new MySqlCommand("SELECT tes FROM ins");

To

MySqlCommand cmd = new MySqlCommand("SELECT tes FROM ins", conn);

And it should work.

Alternatively assign conn to the cmd.Connection property.

The problem with your code is that you never assign a connection to the command, hence the error saying that the connection is not initialized.

Try This

MySqlCommand cmd = new MySqlCommand("SELECT tes FROM ins",conn);

or

MySqlCommand cmd = new MySqlCommand("SELECT tes FROM ins");
cmd.Connection=conn;