private void button1_Click(object sender, EventArgs e)
 {
 click(e);
 
 }

object item = cbLocaties.SelectedItem;


            if (item != null || tbXcor.Text != string.Empty && tbYcor.Text != string.Empty)
            {
                item.ToString();

            }
            else
            {
                Simtimer.Stop();
                MessageBox.Show("ERRROR");

string locatielist = cbLocaties.SelectedItem.ToString();  
           

             if (locatielist == null && tbXcor.Text == string.Empty && tbYcor.Text == string.Empty)
             {
                 Simtimer.Stop();
                 MessageBox.Show("ERROR");
             }