private void Form1_Load(object sender, EventArgs e)
    {
        //check load count...
        int loadCount = ApplicationSettingsDemo.Properties.Settings.Default.LoadCount;
        if (loadCount > 10)
        {
            MessageBox.Show("Trial version expired!");
            this.Close();
        }
    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        try
        {
              ApplicationSettingsDemo.Properties.Settings.Default.LoadCount += 1;
              ApplicationSettingsDemo.Properties.Settings.Default.Save();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message,
                "Failed to save settings",
                MessageBoxButtons.OK,
                MessageBoxIcon.Error);
        }
    }