Get value of control after postback

Question

I have a dynamic control in a page. It was added to this page by codebehind.

FileUpload fu = new FileUpload();
fu.ID = "fu";
fu.EnableViewState = true;
list.Add(fu);

Button btnFu = new Button();
btnFu.Text = "Upload";
btnFu.ID = "btnFu";
list.Add(btnFu);

After using postBack, I can't get the value from this fileUpload.

if (!IsPostBack) {

}
else {
      string str_btn = null;
      if (Request.Form.Keys[Request.Form.Keys.Count - 1] != null)
                    str_btn = Request.Form.Keys[Request.Form.Keys.Count - 1].ToString();
      if (!string.IsNullOrEmpty(str_btn)) 
                    handleClick(str_btn);

}

Anybody has a solution to resolve this?

Do you create them in Page_Load? Do you create them upon a form submission with a PostBack? Where and when exactly? — mostruash, Mar 15 '13 at 04:16
May you access my machine.I will show it more in detail.yes? use teamviewer? — Brian, Mar 15 '13 at 04:17
I'm sorry but I have neither tiemviewer installed on my machine nor I have time for that. You should hire an advisor. — mostruash, Mar 15 '13 at 04:21
I created it isn't in Page_Load.It was created at another side when I press button. — Brian, Mar 15 '13 at 04:28
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/26214/discussion-between-binh-tieu-and-mostruash) — Brian, Mar 15 '13 at 04:50
i think the answers are here and this is a duplicate http://stackoverflow.com/questions/5552243/asp-net-custom-server-control-not-retaining-values-after-post-back — bresleveloper, Aug 12 '14 at 12:42

score 0 · Answer 1 · edited May 23 '17 at 12:31

0

I would try searching for the control using Page.FindControl("fu"). There are some interesting options in the answers to this question covering issues like looking for controls when using masterpages and user controls.

ASP.Net FindControl is not working - How come?

edited May 23 '17 at 12:31

Community

1
1

answered Mar 15 '13 at 03:21

leemicw

612
8
13

Oh,yes,That's it.I used masterpage and ContentPlaceHolder,brother. – Brian Mar 15 '13 at 03:25
I tried but it didn't work.May we make a conversation,brother – Brian Mar 15 '13 at 03:30

score 0 · Answer 2 · answered Mar 15 '13 at 04:39

I suspect the list you have added the controls to is a content container so you must first get a reference to it then call the FindControl("btnFu") method.

// var list = yourListControl
Button btnFu = list.FindControl("btnFu") as Button;
if(btnFu != null)
{
    // Operate on the button
}

score 0 · Answer 3 · answered Mar 15 '13 at 04:41

You need to recreate your dynamically created controls on a post back, I believe.

public class YourPage : System.Web.UI.Page
{
      protected bool AreControlsCreated {
      {
          get{return (bool)ViewState["AreControlsCreated"];}
          set{ViewState["AreControlsCreated"] = value;}
      }

      private void Page_Load(object sender, System.EventArgs e)
      {
          if(!IsPostBack)
          {
              AreControlsCreated = false;
          }
          else if(AreControlsCreated)
          {
              CreateYourControls();
          }
      }

      private void CreateYourControls()
      {
        ...
        FileUpload fu = new FileUpload();
        fu.ID = "fu";
        fu.EnableViewState = true;
        list.Add(fu);

        Button btnFu = new Button();
        btnFu.Text = "Upload";
        btnFu.ID = "btnFu";
        list.Add(btnFu);

        AreControlsCreated = true;
      }

      protected void YourButton_Click(object sender, EventArgs e)
      {
          createYourControls();
      }
}

Hi brother,Thanks for your reply.I see your idea.I believe that it will work fine if we lost control.But in my case,It still show control,But I can't get value from this control.So that,My problem is that can't get value from FileUpload — Brian, Mar 15 '13 at 07:32
How do you try to get the value? Show me your code. You are doing many things wrong including creating controls in behind code. You can put them in the markup as not-visible and make them visible upon a click of a button. Read some books/articles/blogs on best practices. — mostruash, Mar 15 '13 at 10:11

Get value of control after postback

3 Answers3