页面级的继承public partial class Default : BasePage

其他页面要引用的cs

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public class BasePage : System.Web.UI.Page
{
    /// <summary>
    ///
    /// </summary>
    /// <param name="e"></param>
    protected override void OnPreInit(EventArgs e)
    {
        // 这句话加不加就是问题的关键，不会将样式应用到前台，（不加将不会实现，加了能够实现）
        base.OnPreInit(e);
    }

   
  
    /// <summary>
    ///
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void Page_PreInit(object sender, EventArgs e)
    {
        // 是否为空
        if (Session["Theme"] == null)
        {
            // 默认主题
            this.Theme ="Default";
        }
        else
        {
            // 当前选择的主题
            this.Theme = Session["Theme"].ToString();
        }
    }
  
}

 

 Default  页面的cs

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class Default : BasePage //应用了上面的东西
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void ddlSkin_SelectedIndexChanged(object sender, EventArgs e)
    {
        //System.Configuration.ConfigurationManager.AppSettings["Theme"];
        if (!String.IsNullOrEmpty (this.ddlSkin.SelectedValue))
        {
            Session["Theme"] = this.ddlSkin.SelectedValue;
            Response.Redirect("Default.aspx");
        }
    }
     
}