在C＃中监控mysql数据库

Question

In my Visual Studio C# Project, I set up a connection with my mySQL database. Currently there's a timer which executes a method every 0.1 sec. This method checks if a value in my mysql-DB has been changed. If the value changed, a label in my form will be called like the new variable.

Now I want to do this without a timer, so the app should recognize if the value changed by itself. Is this maybe possible with the using of properties?

This is my current code:

private void timer1_Tick(object sender, EventArgs e)
    {
        Dictionary<string, string> humechDictionary = sqlClientHumech.Select("control");
        System.Diagnostics.Debug.WriteLine(humechDictionary);
        var countTest = sqlClientHumech.Count("control");
        System.Diagnostics.Debug.WriteLine(countTest);
        foreach (KeyValuePair<string, string> kvp in humechDictionary)
        {
            System.Diagnostics.Debug.WriteLine("Key = {0}, Value = {1}",
                kvp.Key, kvp.Value);
        }
        var modusValue = humechDictionary["modus"];
        System.Diagnostics.Debug.WriteLine(modusValue);
        if (modusValue == "excel")
        {
            label1.Text = "EXCEL";
        }
        else if (modusValue == "kinect")
        {
            label1.Text = "KINECT";
        }
        else if (modusValue == "manuell")
        {
            label1.Text = "MANUELL";
        }
    }

Answer 1

No, this kind of push notification outbound from the server is not possible with vanilla MySQL. If you're looking for a change in a column value in a DBMS, you need to poll it, as you have been doing.

You could create a user-defined function and call it from a trigger. But this is a perilous approach for lots of reasons.

Here's a decent discussion of the issue. http://karwin.blogspot.com/2006/10/catch-22-of-active-database.html