将JSon发送到ASP.net webmethod并反序列化为一个对象

I have an .aspx page that we are loading UserControls into dynamically at runtime. Each user control has some sort of textbox or combo or some other control. This all works fine. when we go to read the values out of the controls when the user presses search, we cannot do this directlly from C# code behind because the page does not know they are there. my solution is to read the values with JQuery and make an ajax call where I can set the values in a session variable for use when the user gets to the next page. I am having trouble with the JSon specifically. I keep getting the error:I have an .aspx page that we are loading UserCo