How to retrieve the value of a hidden field in ASP.NET after a partial postback

On my ASP.NET page, I am encountering an issue with a hidden field not being found during an asynchronous postback within an update panel. In the updatepanel_Load event, the following code is used:

if (!IsPostBack || triggeredRefresh.Value == "1") 
{
   HiddenField hiddenField = new HiddenField();
   hiddenField.ID ="hiddenField1";
   hiddenField.Value = "0";
   placeHolder1.Controls.Add(hiddenField);
} 
else if ( triggeredCheck.Value == "1" )
{
    HiddenField hiddenField = placeHolder1.FindControl("hiddenField1") as HiddenField;
    var x = Convert.ToInt32(hiddenField.Value);
}

Essentially, hidden fields are added to a placeholder and their values are set with client-side scripting. However, upon an asynchronous postback, the FindControl method returns null because the placeholder1.Controls.Count is 0. This raises the question as to why the count is zero even though the hidden field was added prior to the postback.

Any assistance provided would be greatly appreciated.

javascript.netasp.netasynchronouspostback

Answer №1

Adding controls dynamically may result in them disappearing after postbacks as they do not persist when the page is reloaded. This is due to the fact that they are destroyed during the page lifecycle, as mentioned by Layoric. To ensure the control remains on the page, consider placing it as an inline hiddenfield. Remember that during an ASP.NET page postback, the entire page lifecycle is repeated, including events such as preinit, init, load, prerender, and render.

Answer №2

To access the value of the hidden field, you can utilize this code snippet: 

HttpContext.Request.Form[hiddenField1.UniqueID]
.

Answer №3

What is the reason behind the failure of 

HttpContext.Request.Form["hiddenField1"]
?

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