How do i render a control to a string

I've seen it time and time again the typical answer being something like this:

public string RenderControlToHtml(Control ControlToRender)
{
    System.Text.StringBuilder sb = new System.Text.StringBuilder();
    System.IO.StringWriter stWriter = new System.IO.StringWriter(sb);
    System.Web.UI.HtmlTextWriter htmlWriter = new System.Web.UI.HtmlTextWriter(stWriter);
    ControlToRender.RenderControl(htmlWriter);
    return sb.ToString();
}

... This is fine if you have simple html tags but when I have a textbox or some other asp control in my control it throws a wobbly about the control not being on a form (which in fact it is because im trying to render a portion of the page to a string that i can then send as an email)

So ...

I'm pretty sure this has been asked and answered before but i'm at a loss for finding a real answer that actually works ...

How do i render the html output of both server and client side controls to a html string in .Net 4.0 because seemingly the above is not good enough?

Note:

I have found examples that tal开发者_运维技巧k about doing this at page level ...

public override void VerifyRenderingInServerForm(Control control)
{
    //Do nothing (we dont care if theres a form or not)
}

... and disabling event validation but apparently that's not working for me either.

Is there a way to do this without a "hack" thats clean?

Also:

I even tried creating a new page, adding a form to it, added my control to that then calling renderControl on that page to which i got more errors.

EDIT: I've been digging around and I think the problem might be related to postbacks or something because i found this: http://forums.asp.net/t/1325559.aspx

Another thing that might be putting a bit of a spanner in the works is my use of the ajax toolkit, I essentially need only the visible portion of the control which seems to give a bit of a headache for updatepanels for some reason.

I'm guessing the above sample works only on basic .net controls that are not ajax toolkit related.

What further complicates the issue is that I would like to get the control in its current state when a button is clicked at the bottom of it ...

Essentially the control represents a form for booking an MOT and I would like to render the form filled in to an email that is then sent to the garage if that makes sense.

I'm thinking i may have to admit defeat here and simply get the markup from the client and manually build an email pulling out the control values as this seems to be a compatability issue between ajax controls and the renderControl method from what i can tell (maybe you cant render a partial postback compatible control in this fashion).

Unless someone smarter than me can prove it can be done ???

---

Create an ajax control extender and get the html markup on the client side then post that back to the server for processing, it's a bit of hack but it seems that anything involving ajax controls will cause the default recommended mechanism to break.