title: Get value of control after postback
body: <p>I have a dynamic control in a page. It was added to this page by codebehind.</p>
  
  <pre><code>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);
  </code></pre>
  
  <p>After using postBack, I can't get the value from this fileUpload.</p>
  
  <pre><code>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);
  
  }
  </code></pre>
  
  <p>Anybody has a solution to resolve this?</p>