动态添加控件时代码的最佳程度

在我正在设计的网站中，我需要显示我使用 asp：FileUpload 控件上传的图像。因此，上传后，我使用字符串生成器添加div，img和textarea，然后将其加载到我已经创建的面板中。那么使用Stringbuilder加载内部HTML更好，还是使用HtmlgenericControls添加图像和文本区域等控件更好。我正在使用 C#。我目前的编码方式如下：

前端：

<form id="form1" runat="server">
<div class="transbox" id="mainbk" runat="server" style="position:absolute; top:0px; left:0px; width: 100%; height: 100%;" >
  <asp:FileUpload runat="server" ID="UploadImages" style="background-color:white; position:absolute; font-family:'Palatino Linotype'; font-size:medium; top: 4px; left: 350px; right: 251px;" Width="500px" AllowMultiple="true"/>
    <asp:Button runat="server" ID="uploadedFile" style="position:absolute;  font-family:'Palatino Linotype'; font-size:medium; top: 4px; left: 870px; width: 112px; height: 29px;" Text="Upload" OnClick="uploadFile_Click" />
    <asp:Panel ID="updtpanel" runat="server" CssClass="transbox" style="width:100%;height:100%;left:0px;top:0px;position:absolute" Visible="false">
    </asp:Panel>
 </div>

</form>

后端如下：

protected void uploadFile_Click(object sender, EventArgs e)
{
    if (UploadImages.HasFiles)
    {
       int tid = 0;
       string fileExt = Path.GetExtension(UploadImages.FileName).ToLower();
       if (fileExt == ".jpeg" || fileExt == ".png" || fileExt == ".jpg" || fileExt == ".bmp")
       {
           HtmlGenericControl d = new HtmlGenericControl("div");
           Button btnsave = new Button();
           btnsave.Text = "Save";

           sb.Append("<div class=" + "'"savback'"" + ">");
           sb.Append("<div class=" + "'"head'"" + ">Write Description</div>");
           foreach (HttpPostedFile uploadedFile in UploadImages.PostedFiles)
           {
               id += 1;
               tid = tid + 1;
               string textid = "txt" + tid;
               filepath = Server.MapPath("~/Images/Gallery/" + uploadedFile.FileName);
               uploadedFile.SaveAs(filepath);
               newpath = "../Images/Gallery/" + uploadedFile.FileName;
               try
               {
                   updtpanel.Visible = true;
                   sb.Append("<div class=" + "'"dataload'"" + ">");
                   sb.Append("<img class=" + "'"loadimg'"" + "src=" + "'"" + newpath.ToString() + "'"" + " />");
                   sb.Append("<textarea  class=" + "'"txtdes'"" + "id=" + "'"" + textid + "'"" + "></textarea>");
                   sb.Append("</div>");

               }
               catch (Exception ex)
               {
                   Response.Write(ex.Message);
               }
           }
           sb.Append("</div>");
           d.InnerHtml = sb.ToString();
           updtpanel.Controls.Add(d);
           updtpanel.Controls.Add(btnsave);
       }
       else
       {
           Page.ClientScript.RegisterStartupScript(GetType(), "msgbox", "alert('Please Select only Image Files!!');", true);
       }
    }
    else
    {
        Page.ClientScript.RegisterStartupScript(GetType(), "msgbox", "alert('Please Select a File First!!');", true);        
    }
}

请让我知道哪种是创建动态控件的好方法？