Reg: Microsoft Chatbot: Passing userId/name in the iFrame SRC and reading that in the C# BOT code at server side

Question

I am passing the userId from the iFrame like below, and this iFrame is embedded on the master screen of our website.

iframe src="https://webchat.botframework.com/embed/BotId?s=BOTSecret&userid=" + <%=UserId %> + height="400"

and trying to read it from the bot code like below, which is called from the StartAsync method

userid = context.Activity.From.Id;

But I get some junk values into the userId, and when I do the F12 into the iFrame, I do see the proper userid appended to the iframe src.

Any suggestions on where I am going wrong will be highly appreciated. Thanks.