1. 添加CSS样式: Style style = new Style();

                       style.ForeColor = System.Drawing.Color.Navy;

                       style.BackColor = System.Drawing.Color.LightGray;

                       this.Header.StyleSheet.CreateStyleRule(style, null, "body");

 

2. 链接外部的CSS样式表: HtmlLink link = new HtmlLink();

                                   link.Attributes.Add("type", "text/css");

                                   link.Attributes.Add("rel", "stylesheet");

                                   link.Attributes.Add("href", "~/newstyle.css");

                                   this.Header.Controls.Add(link);

方法3   aa.aspx.cs   public   string   m_StyleSrc   =   string.Empty; //公共变量  ,样式文件路径       

                              private   void   Page_Load(object   sender,   System.EventArgs   e)     {             

                               m_StyleSrc   =  "../xxx.css";  //页面加载时赋值      }   

                               }          

           aa.aspx      <LINK   href="<%=m_StyleSrc%>"   type="text/css"   rel="stylesheet">

 

方法4 下面这个方法没试过,不知是否能用  

                 protected void Page_Onload(object sender, EventArgs e)     {

                                          Page.StyleSheetTheme = "../css/infomore.css";

                                         }

方法5   页面：

                   <link   href=""   rel="stylesheet"   type="text/css"     id="css"   runat="server"/> 

          后台  

                   this.css.Href   =   "css文件路径";