public partial class Form1: Form
    {
        private void btnOpen_Click(object sender, EventArgs e)
        {
            FrmCorpDTAdd fd = new FrmCorpDTAdd(dsService);
            if (fd.ShowDialog() == DialogResult.Cancel)  //打开子窗体，并且关闭后
            {
                RetRowGuid = fd._RetRowGuid;    //此处接收子窗体的值
            }
         }
     }

    public partial class Form2 : Form
    {
        public string _RetRowGuid;      //定义共有的全局变量方便其他窗体访问,记录返回到父窗体的值
       private void btnSave_Click(object sender, EventArgs e)　　
        {
            _RetRowGuid = dgSG_AptitudeProject.CurrentRow.Cells["RowGuid"].Value.ToString();    //dataGridView选中行的RowGuid值赋给全局变量_RetRowGuid
            this.DialogResult = DialogResult.Cancel;        //取消(关闭)
        }
     }