C# WINFORM窗体右上角X点击后无法退出调试

这个是由于你的程序在运行过程中开启了新线程，而在结束时没有把线程退出

    private void BtnUpdate_Click(object sender, EventArgs e)
    {
      int iX = this.Left;
      int iY = this.Top;
      Thread thr = "更新".FindAndMoveMsgBox(iX, iY, true);
      if (dgv.SelectedRows.Count == 0)
      {
        "请先选择行才能进行更新".showAlert("更新");
        return;
      }
      else
      {
        iRow = dgv.SelectedRows[0].Index;
        SelectRow();
      }
      iState = 2;
      frm.Text = "更新行";
      frm.SetFrmCenter(this.ParentForm);
      frm.ShowDialog();
      thr.Abort();
    }