private void btnAddCategory_Click(object sender, EventArgs e)
 {
     if (verifyStringToBeAdded(cbbCategory.Text, cbbCategory.Items.Cast<String>()))
     {
         DaoVideo daoVideo = new DaoVideo();
         daoVideo.openConnection(this.GetType(), "sqlErrorHandler");
         daoVideo.insertCategory(cbbCategory.Text, this.GetType(), "sqlErrorHandler");
         daoVideo.closeConnection();
         loadCategories();
         updateLbCategory();
     }
     cbbCategory.Focus();
 }