C# 動態產生的textbox怎樣擷取值

在頁面page_load中：

 int num = 0;
                    for (int i = 0; i < dt_data.Rows.Count; i++)
                    {
                        dgv.Rows.Add();
                        int n = dgv.Rows.Count - 1;
                        for (int j = 2; j < dt_data.Columns.Count; j++)
                        {

                            int hor = num / 3;
                            int ver = num % 3;
                            TextBox txt = new TextBox();
                            txt.Location = new Point(hor * 327 + 139, ver * 35 + 26);
                            txt.Size = new Size(130, 29);
                            txt.Text = dt_data.Rows[i].ItemArray[j].ToString();

//在頁面的groupBox2中天劍TextBox；
                            this.groupBox2.Controls.Add(txt);                       
                            num++;
                        //    dgv.Rows[n].Cells[j - 2].Value = dt_data.Rows[i].ItemArray[j].ToString();
                        }
                        n++;
                    }

在取值的時候這樣設定：

 foreach (Control c in this.groupBox2.Controls)
            {
                if (c is TextBox )
                {                      //你要取得的值
                    string s = ((TextBox)c).Text;                  // 給textBox中重新附值
                    ((TextBox)c).Text = "1111";
                  
                }
            }