我有以下代码:
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
public class SignalRHub : Attribute
{
public readonly string Route;
public SignalRHub(string Route)
{
this.Route = Route;
}
}
[SignalRHub("hubpath")]
public class TestHub : Hub
{
...
}
这定义了一个SignalR集线器,其中包含一个知道路径的属性。
我想动态地注册带有SignalRHub属性的集线器,所以我有以下代码来查找所有集线器:
// find all hubs
var Hubs =
from Assemblies in AppDomain.CurrentDomain.GetAssemblies().AsParallel()
from Types in Assemblies.GetTypes()
let Attributes = Types.GetCustomAttributes(typeof(SignalRHub), true)
where Attributes?.Length > 0
select new { Type = Types };
var HubsList = Hubs.ToList();
然后我想注册它们,但这是我遇到问题的地方:
foreach (var H in HubsList)
{
// get the route attribute
var Route = string.Empty;
var Attributes = Attribute.GetCustomAttributes(H.Type);
foreach (var Attribute in Attributes)
{
if (Attribute is SignalRHub A)
{
Route = A.Route;
break;
}
}
// register the hub
if (string.IsNullOrEmpty(Route))
{
Logging.Warn($"[Hub] {H.Type.Name} does not have a path, skipping");
}
else
{
Logging.Info($"[Hub] Registering {H.Type.Name} with path {Route}");
Application.UseSignalR(R => R.MapHub<H>(Route)); <- this won't compile
}
MapHub要求T从Hub派生;如果H是TestHub类型,它应该没问题,但该语法不起作用。
我怎样才能做到这一点?
我的解决方案(使用反射)
using System;
using System.Reflection;
using Microsoft.AspNetCore.SignalR;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Connections;
//somewhere in your code
private static readonly MethodInfo mapperMethodInfo =
typeof(HubRouteBuilder).GetMethod(
"MapHub",
new Type [] {
typeof(PathString)
},
null
);
// in your mapping code
// replace this:
Application.UseSignalR(R => R.MapHub<H>(Route));
// with this
Application.UseSignalR(R =>
{
// pay attention to use of H.Type, R and Route variables
mapperMethodInfo.MakeGenericMethod(H.Type).Invoke(R, new object [] { Route });
});
编译器不满意,因为您使用实例变量作为泛型类型。
因为H实例变量指向Hub实例,所以可以替换:
Application.UseSignalR(R => R.MapHub<H>(Route))
通过:
Application.UseSignalR(R => R.MapHub<Hub>(Route))