从Request.Url中获取根网址的简单操作

var uri = Request.Url.Scheme + "://" + Request.Url.Host + "/userfile/img";

var uri = Request.Url.GetLeftPart(UriPartial.Authority) + "/userfile/img";

https://git.oschina.net/userfile/img

//获取当前页面url 
string myurl = System.Web.HttpContext.Current.Request.Url.ToString();
 
//获取上一页面url
string UrlReferrer = System.Web.HttpContext.Current.Request.UrlReferrer.ToString();

"http://"是协议名
"www.test.com"是域名
"aaa"是站点名
"bbb.aspx"是页面名（文件名）
"id=5&name=kelli"是参数
   
//获取 完整url （协议名+域名+站点名+文件名+参数）
string url = Request.Url.ToString();
url = "http://www.test.com/aaa/bbb.aspx?id=5&name=kelli";
 
//获取 站点名+页面名+参数：
string url = Request.RawUrl;
string url = Request.Url.PathAndQuery;
url= "/aaa/bbb.aspx?id=5&name=kelli";
 
//获取 站点名+页面名：
string url = Request.Url.AbsolutePath;
string url = Request.Path;
url= "aaa/bbb.aspx";
 
//获取 域名：
string url = Request.Url.Host;
url= "www.test.com";
 
//获取 参数：
string url = Request.Url.Query;
url= "?id=5&name=kelli";
 
//如果有端口的话
int port = System.Web.HttpContext.Current.Request.Url.Port;