How do I get the HTML output of a UserControl in .NET (C#)?

Question

If I create a UserControl and add some objects to it, how can I grab the HTML it would render?

ex.

UserControl myControl = new UserControl();
myContr         


        

Answer 1

Seven years late, but this deserves to be shared.

The generally accepted solution - StringBuilder into StringWriter into HtmlWriter into RenderControl - is good. But there are some gotchas, which I unfortunately ran across while trying to do the same thing. Some controls will throw errors if they're not inside of a Page, and some will throw errors if they're not inside of a

with runat="server". The ScriptManager control exhibits both of these behaviours.

I eventually found a workaround here. The gist of it is basically just instantiating a new Page and Form before doing the writer work:

Page page = new Page();
page.EnableEventValidation = false;

HtmlForm form = new HtmlForm();
form.Name = "form1";
page.Controls.Add(form1);

MyControl mc = new MyControl();
form.Controls.Add(mc);

StringBuilder sb = new StringBuilder();
StringWriter sw = new StringWriter(sb);
HtmlTextWriter writer = new HtmlTextWriter(sw);

page.RenderControl(writer);

return sb.ToString();

Unfortunately, this gives you more markup than you actually need (since it includes the dummy form). And the ScriptManager will still fail for some arcane reason I haven't puzzled out yet. Honestly, it's a whole lot of trouble and not worth doing; the whole point of generating controls in the code-behind is so that you don't have to fiddle around with the markup, after all.