c# 删除文件

string url = Server.MapPath("p_w_picpath/bg.gif");
        if (!File.Exists(url))
        {
            ClientScript.RegisterStartupScript(GetType(), "", "alert('文件不存在！');", true);
        }
        else
        {
            File.Delete(url);
            ClientScript.RegisterStartupScript(GetType(), "", "alert('文件已删除！');", true);
        }