I have a hidden asp.net control which gets written to via JavaScript and contains a JSON string of a collection of data. A user is given options and can add to the collection via client side events. If a user decides to upload a file after they have selected items for this collection, the data is no longer present.  Why is this data getting wiped after an AJAX upload control post back? If I do a simple btnClick event, the JSON is always available on the server side, but the upload component’s post back seems to clear the variable.  I can also get the value of the control from inside the  Uploader_FileUploaded event, but when the page reloads, it's blank.