Unable to serialize the session state using asyncfileupload.

Question

Error:-

Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.

Note: I am using State Server mode. and trying to store Control in session:-

 

if (asyUpldOffer.HasFile)

{

string contentType = asyUpldOffer.ContentType;

if (contentType == "application/vnd.openxmlformats-officedocument.wordprocessingml.document" || contentType == "application/pdf" || contentType == "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" || contentType == "application/msword" || contentType == "image/jpeg" || contentType == "image/jpg")

{

Session["UploadOffer"] = asyUpldOffer;

}

else

{

Session["UploadOffer"] = null;

}

}