Okay, here is the solution I am currently using :
I created a helper class :
using System.Web.UI;
using System.Web.UI.WebControls;
namespace BusinessLogic.Helper
{
public class CssAdder
{
public static void AddCss(string path, Page page)
{
Literal cssFile = new Literal() { Text = @"<link href=""" + page.ResolveUrl(path) + @""" type=""text/css"" rel=""stylesheet"" />" };
page.Header.Controls.Add(cssFile);
}
}
}
and then through this helper class, all I have to do is :
CssAdder.AddCss("~/Resources/Styles/MainMaster/MainDesign.css", this.Page);
CssAdder.AddCss("~/Resources/Styles/MainMaster/MainLayout.css", this.Page);
CssAdder.AddCss("~/Resources/Styles/Controls/RightMainMenu.css", this.Page);
//...
So I can add as much as I want with one line of simple code.
It also works with Masterpage and content page relationships.
Hope it helps.
P.S: I don’t know the performance difference between this and other solutions but it looks more elegant and easy to consume.