使用SignalR技术实现监控刷新功能

我是CHARSET，转载请保留全文本。

建立POCO

public class Eventing : EventArgs {
  public DateTime EmitTime { get; set; }
  public string? Message { get; set; }
}

public class SampleEvent : Eventing {
  public int Success { get; set; }
  public int Fail { get; set; }
}

建立能发送SignalR的服务接口

public interface ICacheQueueService<T> where T: EventArgs {
  Task AddThenSend(T t);
  List<T> Get();
}

public interface ICacheObjectService<T> where T: EventArgs {
  Task UpdateThenSend(T t);
  T Get();
}

实现接口

public class CacheQueueService<T> : ICacheQueueService<T> where T: EventArgs {
  readonly ConcurrentQueue<T> events = new();
  readonly IHubContext<Whisper> hubContext;
  readonly int queueDepth = 20;
  readonly string name = $"{nameof(CacheQueueService<T>)}<{typeof(T).Name}>";
  
  //忽略DI过程
  
  public async Task AddThenSend(T t) {
    events.Enqueue(t);
    while (events.Count > queuDepth) event.TryDequeue(out var _);
    await hubContext.Clients.All.SendAsync(name, t);
  }
  
  public List<T> Get() => events.ToList();
}

public class CacheObjectService<T> : ICacheObjectService<T> where T: EventArgs {
  //同上
  readonly string name = $"{nameof(CacheObjectService<T>)}<{typeof(T).Name}>";
  readonly T _t = new();
  readonly EmitCloneService clone;
  
  public async Task UpdateThenSend(T t) {
    clone.Clone(T, _t);
    await hubContext.Clients.All.SendAsync(name, t);
  }
}

关于EmitCloneService

public class EmitCloneService {
  readonly Dictionary<Type, Delegate> cachedIL = new();
  
  public void Clone<T>(T source, T target) {
    if (source is null || target is null) return;
    var type = typeof(T);
    if (!cachedIL.TryGetValue(type, out var @delegate)) {
      var dynamicMethod = new DynamicMethod("Clone", null, new[] { type, type });
      var il = dynamicMethod.GetILGenerator();
      foreach(var property in type.GetProperties()) {
        if (property.CanRead && property.CanWrite && !property.GetAccessor(true)[0].IsStatic) {
          il.Emit(OpCodes.Ldarg_1);
          il.Emit(OpCodes.Ldarg_0);
          il.Emit(OpCodes.Callvirt, property.GetMethod);
          il.Emit(OpCodes.Callvirt, property.SetMethod);
        }
      }
      il.Emit(OpCodes.Ret);
      var clone = (Action<T, T>)dynamicMethod.CreateDelegate(typeof(Action<T, T>));
      cachedIL.Add(type, clone);
      clone(source, target);
    } else {
      ((Action<T, T>)@delegate)(source, target);
    }
  }
}

注册服务

services.AddSingleton<ICacheObjectSerivce<SampleEvent>, CacheObjectService<SampleEvent>>();

编写Razor页面（页面组件使用AntDesign Blazor）

@inject ICacheObjectService<SampleEvent> Sample
//...
<Card Title="Sample" Style="width:300px">
  <Extra>@Sample.EmitTime</Extra>
  <Body>
  	<Badge Count=@Sample.Success ShowZero Style="background-color:limegreen" />
    <Badge Count=@Sample.Fail ShowZero Style="background-color:orangered" />
  </Body>
</Card>
//...

在Razor页面的操作

readonly SampleEvent Sample = new();
protected override async Task OnInitializedAsync() {
  hubConnection = new HubConnectionBuilder().WithUrl(NavigationManager.ToAbsoluteUri("/whisper")).Build();
  var sampleEventName = $"{nameof(CacheObjectService<T>)}<{nameof(SampleEvent)}>";
  hubConnection.On<SampleEvent>(name, sample => {
    Sample.EmitTime = sample.EmitTime;
    Sample.Success = sample.Success;
    Sample.Fail = sample.Fail;
  });
}