For Each c As Control In Me.Controls 
            If c Is TextBox Then 
                Select Case c.ClientID 
                    Case "TextBox1" 
                        DirectCast(c, TextBox).Text = "a1" 
                    Case "TextBox2" 
                        DirectCast(c, TextBox).Text = "a2" 
                    Case "TextBox3" 
                        DirectCast(c, TextBox).Text = "a3" 
                End Select 
            End If 
        Next

------解决方案--------------------
string id = string.Empty;
           string controlID = string.Empty;
           for (int i = 0; i < this.Controls.Count; i++)
           {
               foreach (System.Web.UI.Control control in this.Controls[i].Controls)
               {
                   if (control is TextBox)
                   {
                       controlID = (control as TextBox).ID;
                       string[] textBoxHeads = textBoxHead.Split(',');
                       for (int j = 0; j < textBoxHeads.Length; j++)
                       {
                           if (controlID.IndexOf(textBoxHeads[j]) == 0)
                           {
                               id = controlID.Substring(textBoxHeads[j].Length);
                               if (dt.ContainCol(id))
                               {
                                   //try
                                   //{
                                   (control as TextBox).Text = dt.GetValue(id).Trim();
                                   //}
                                   //catch
                                   //{
                                   //}
                               }
                           }
                       }

                   }
                   else if (control is HtmlInputHidden)
                   {
                       controlID = (control as HtmlInputHidden).ID;
                       string[] valueListHeads = hiValueHead.Split(',');
                       for (int j = 0; j < valueListHeads.Length; j++)
                       {
                           if (controlID.IndexOf(valueListHeads[j]) == 0)
                           {
                               id = controlID.Substring(valueListHeads[j].Length);
                               if (dt.ContainCol(id))
                               {
                                   (control as HtmlInputHidden).Value = dt.GetValue(id).Trim();
                               }
                           }
                       }
                   }
                   else if (control is HtmlInputText)
                   {
                       controlID = (control as HtmlInputText).ID;
                       string[] valueListHeads = hiValueHead.Split(',');
                       for (int j = 0; j < valueListHeads.Length; j++)