All Web controls have a RenderControl(HtmlTextWriter) method that, when invoked, renders the control, emitting its resulting markup to the passed-in HtmlTextWriter instance.
This programmatic rendering is performed using the following code:
StringBuilder SB = new StringBuilder();
StringWriter SW = new StringWriter(SB);
HtmlTextWriter htmlTW = new HtmlTextWriter(SW);
WebControlToRenderID.RenderControl(htmlTW);
After the above code is executed, the control's rendered HTML can be accessed from the StringBuilder object's ToString() method (i.e., SB.ToString()).
In ASP.NET 1.x, this code works wonderfully unless the Web control being rendered is a control that must reside within a WebForm or contains a child control that must reside in a WebForm. For example, Button Web controls must reside within a WebForm. Consequently, if you attempt to use the above code to render a Button Web control or a DataGrid or GridView that contains a Button (or LinkButton or ImageButton) Web control, an exception will be raised complaining that the control is not in a WebForm.
Sending the Rendered Control's Markup in an Email Message
Once the control's markup has been rendered and stored in a string, we're ready to email it to a specified recipient. Simply send an HTML-formatted email using ASP.NET 2.0's MailMessage and SmtpClient classes in the System.Net.Mail namespace