C# MapPageRoute-can'；在中间发送空字符串？

在我维护的一个项目的Global.asax.cs中，有一个方法如下所示

private static void MapRouteWithName(string name, string url, string physicalPath, bool? checkPhysicalUrlAccess = null, RouteValueDictionary defaults = null)
{
  Route route;
  if ((checkPhysicalUrlAccess != null) && (defaults != null))
  {
    route = System.Web.Routing.RouteTable.Routes.MapPageRoute(name, url, physicalPath, checkPhysicalUrlAccess.Value, defaults);
  }
  else
  {
    route = System.Web.Routing.RouteTable.Routes.MapPageRoute(name, url, physicalPath);
  }
  route.DataTokens = new RouteValueDictionary();
  route.DataTokens.Add("RouteName", name);
}

然后在Global.asax.cs中使用它设置如下路由：

MapRouteWithName("Change User", "User/Change/{id}/{organizationid}/{username}/{logonaccount}/{phone}", "~/User/Change.aspx", true,
  new RouteValueDictionary { { "id", "0" }, { "organizationid", "0" }, { "username", "" }, { "logonaccount", "" }, { "phone", "" } });

Response.RedirectToRoute("Change User", new
{
  id = userID,
  organizationid = selectedOrganizationID,
  username = userName,
  logonaccount = logonAccount,
  phone = phone
});

routes.MapPageRoute(
    routeName: "ChangeUser1",
    routeUrl: "User/Change/{id}/{organizationid}/{username}/{logonaccount}/{phone}",
    physicalFile: "~/User/Change.aspx",
    checkPhysicalUrlAccess: true,
    defaults: new RouteValueDictionary(new {
        phone = UrlParameter.Optional,
    })
);

routes.MapPageRoute(
    routeName: "ChangeUser2",
    routeUrl: "User/Change/{id}/{organizationid}/{username}",
    physicalFile: "~/User/Change.aspx",
    checkPhysicalUrlAccess: true,
    defaults: new RouteValueDictionary(new
    {
        username = UrlParameter.Optional
    })
);

然后在页面后面的代码中可以找到如下内容：

MapRouteWithName("Change User", "User/Change/{id}/{organizationid}/{username}/{logonaccount}/{phone}", "~/User/Change.aspx", true,
  new RouteValueDictionary { { "id", "0" }, { "organizationid", "0" }, { "username", "" }, { "logonaccount", "" }, { "phone", "" } });

Response.RedirectToRoute("Change User", new
{
  id = userID,
  organizationid = selectedOrganizationID,
  username = userName,
  logonaccount = logonAccount,
  phone = phone
});

routes.MapPageRoute(
    routeName: "ChangeUser1",
    routeUrl: "User/Change/{id}/{organizationid}/{username}/{logonaccount}/{phone}",
    physicalFile: "~/User/Change.aspx",
    checkPhysicalUrlAccess: true,
    defaults: new RouteValueDictionary(new {
        phone = UrlParameter.Optional,
    })
);

routes.MapPageRoute(
    routeName: "ChangeUser2",
    routeUrl: "User/Change/{id}/{organizationid}/{username}",
    physicalFile: "~/User/Change.aspx",
    checkPhysicalUrlAccess: true,
    defaults: new RouteValueDictionary(new
    {
        username = UrlParameter.Optional
    })
);

现在，这在大多数情况下都能很好地工作，但在这个特定的示例中，我不知道变量userName、logonAccount和phone是否确实包含某些内容，或者是空的。例如，当userName为空（“”）且logonAccount具有值（“abcde”）时，将引发异常：

System.InvalidOperationException: No matching route found for RedirectToRoute.

---

当在具有值的变量之间有一个空字符串的变量时，似乎会引发异常。（这有意义吗？）对此我能做些什么？

这里的问题是重定向与路由不匹配，因为您错误地声明了可选值。使其成为可选的唯一方法是采用如下配置：

MapRouteWithName("Change User", "User/Change/{id}/{organizationid}/{username}/{logonaccount}/{phone}", "~/User/Change.aspx", true,
  new RouteValueDictionary { { "id", "0" }, { "organizationid", "0" }, { "username", "" }, { "logonaccount", "" }, { "phone", "" } });

Response.RedirectToRoute("Change User", new
{
  id = userID,
  organizationid = selectedOrganizationID,
  username = userName,
  logonaccount = logonAccount,
  phone = phone
});

routes.MapPageRoute(
    routeName: "ChangeUser1",
    routeUrl: "User/Change/{id}/{organizationid}/{username}/{logonaccount}/{phone}",
    physicalFile: "~/User/Change.aspx",
    checkPhysicalUrlAccess: true,
    defaults: new RouteValueDictionary(new {
        phone = UrlParameter.Optional,
    })
);

routes.MapPageRoute(
    routeName: "ChangeUser2",
    routeUrl: "User/Change/{id}/{organizationid}/{username}",
    physicalFile: "~/User/Change.aspx",
    checkPhysicalUrlAccess: true,
    defaults: new RouteValueDictionary(new
    {
        username = UrlParameter.Optional
    })
);

当最后3个参数中的任何一个不在重定向范围内时，这将始终有效但是，有一个问题-当您省略一个参数时，右侧的所有参数也将为空。这就是内置路由的工作方式。参数只有在其右侧没有值时才可以是可选的

如果希望所有3个参数都是可选的，并且不必担心参数传递的顺序或组合，则有2个选项：

使用查询字符串参数

使用约定建立一系列路线，如中所示

---

在处理具有大量可选参数的搜索表单时，查询字符串参数是一个简单得多的选项，因为它们可以以任意顺序和任意组合提供，而无需做任何额外的工作。它们自然适合这种情况。

用户需要有名字吗？如果是，这种情况意味着什么？变量userName、logonAccount和phone实际上是搜索词。这里发生的事情是，显示了现有用户的列表，并单击其中一个用户以进行更改。这三个变量随后不会在更改页面的表单中使用，而是为了能够返回到列表页面，就像在单击用户之前看到的那样。如果有人搜索了每个包含“abcde”的用户名，那么应该恢复特定的列表。