asp.net - Failed to load viewstate. The control tree into which viewstate is being loaded

Question

I am receiving the following error message after an HTTP POST on an ASP.NET form hosted inside a UserControl:

Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request. For example, when adding controls dynamically, the controls added during a post-back must match the type and position of the controls added during the initial request.

Here's additional info:

• I'm running .NET 4.5 RC
• It's an Umbraco 4.7-based website
• On my local dev machine the form works perfectly
• This error only occurs on the staging server which has .NET 4.5 (only), MSSQL 2012 Express, IIS 7.5, Windows 7 (I know, it's not a real server yet, one day maybe...)
• The server is not part of a web farm (or garden, tho that should be irrevelant)
• The user control does render controls dynamically

I have applied all the latest service packs. I have run out of ideas now! I have even restarted it and also performed a richual over the server involving a song and a special dance to no avail.

Answer 1

What is important when you are adding controls dynamically is on which event you are adding them.

If you added controls on events that occur after load, they will be part of the viewstate you send to the client.

You will have to add those controls again before LoadViewState is called.

If you run into cases where the decision of which controls to add is itself stored in the ViewState or the value of a control, then remember even before the ViewState is loaded, this data is available in Request.Params

Refer the asp.net page life cycle