使用反射獲取具有特定屬性值的方法

Question

我有這個代表：

 public delegate void PacketHandler(Client client, Packet packet);

我有這個屬性：

[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
public sealed class PacketHandlerAttribute : Attribute
{
    public ServerType Server { get; private set; }
    public int Code { get; private set; }

    public PacketHandlerAttribute(ServerType server, int code)
    {
        this.Server = server;
        this.Code = code;
    }
}

我想根據給定的ServerType值創建一個方法來返回IEnumerable<Tuple<PacketHandlerAttribute, PacketHandler>> 。 因此，如果我使用ServerType.Server調用此方法，它將返回所有包含Server1作為其屬性的方法。

到目前為止，我做到了：

public static IEnumerable<Doublet<PacketHandlerAttribute, PacketHandler>> GetPacketHandlers(ServerType server)
    {
        foreach (Type type in Assembly.GetExecutingAssembly().GetTypes())
        {
            foreach (MethodInfo method in type.GetMethods())
            {
                PacketHandlerAttribute attribute = (PacketHandlerAttribute)method.GetCustomAttribute(typeof(PacketHandlerAttribute));

                if (attribute != null)
                {
                    if (attribute.Server == server)
                    {
                        yield return new Doublet<PacketHandlerAttribute, PacketHandler>(attribute, (PacketHandler)Delegate.CreateDelegate(typeof(PacketHandler), method));
                    }
                }
            }
        }
    }

我想問一下這是否是正確的方法，而LINQ如何縮短它呢？

Answer 1

我認為這會有所幫助。

 var methods = from type in assembly.GetTypes()
                      from method in type.GetMethods()
                      let attribute = method.GetCustomAttributes(typeof(PacketHandlerAttribute), false).Cast<PacketHandlerAttribute>().FirstOrDefault()
                      where attribute?.Code == 1
                      select new { method, attribute };

你的方法

public IEnumerable<(PacketHandlerAttribute attribute, PacketHandler handler)> GetPacketHandlers(ServerType server)
        {
            var assembly = Assembly.GetEntryAssembly();

            return from type in assembly.GetTypes()
                          from method in type.GetMethods()
                          let attribute = method.GetCustomAttributes(typeof(PacketHandlerAttribute), false).Cast<PacketHandlerAttribute>().FirstOrDefault()
                          where attribute?.Server == server
                          select (attribute, (PacketHandler)method.CreateDelegate(typeof(PacketHandler)));
        }