Asp.Net: Embed CSS in server control's assembly.

Question:

How to embed a CSS file in a server control assembly?
How to access style information (CSS) from a server control assembly?

Answer:

The style sheet file (CSS) must be an embedded resource. (right-click on the file and set Build Action to Embedded Resource.)

Follow these steps:

1. Register a WebResource for the CSS file in the AssemblyInfo.cs

   ...
   [assembly: System.Web.UI.WebResource("MyControlStyle.css", "text/css")];
   ...
   

2. Add Stylesheet include to the header of the page

   string styleLink= "<link rel='stylesheet' text='text/css' href='{0}' />";
   string location = Page.ClientScript.GetWebResourceUrl(this.GetType(), "MyControlStyle.css");
   LiteralControl styleInclude = new LiteralControl(String.Format(styleLink, location));
   ((HtmlControls.HtmlHead) Page.Header).Controls.Add(styleInclude );
   

   If you like the AjaxControlToolkit, you can have the second step in one line. (Include the AjaxControlToolkit.dll and namespace).
   Then add the ClientCssResource attribute to your main control class.

   ...
   [ClientCssResource("MyNameSpace.MyFolder.MyControlStyle.css")]
   ...
   

   In the Prerender event handler call the RegisterCssReference method of the static class ScriptObjectBuilder which is part of the AjaxControlToolkit

   ...
   ScriptObjectBuilder.RegisterCssReferences(this);
   ...
   

All resources embedded within an assembly will be included into the client page through a WebResource.axd request with a funny looking URL. But that should be transparent to you.