private void bindingNavigatorDeleteItem_Click(object sender, EventArgs e)
 {
     if (dataGridView1.CurrentRow == null)
     {
         return;
     }
     if (MessageBox.Show("是否要删除这条数据?", "请选择", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
     {
         int user_id = int.Parse(dataGridView1.CurrentRow.Cells["userId"].Value.ToString());
         if (user_id == 2)
         {
             MessageBox.Show("默认用户禁止删除!");
             return;
         }
         if (db.DeleteUser(user_id) != 0)
         {
             dataGridView1.Rows.Remove(dataGridView1.CurrentRow);
             return;
         }
         MessageBox.Show("删除失败!");
     }
 }