我正在使用 Microsoft.AspNetCore.SignalR.Client 从我的 WebAPI 项目打开一个连接，以连接和调用我的 SignalR Hub 项目中的方法。这些是托管在不同服务器上的不同项目。
如何检查连接是否已经启动，不尝试启动两次？
我使用以下代码从 WebAPI 连接:
public class ChatApi
{
private readonly HubConnection _connection;
public ChatApi()
{
var connection = new HubConnectionBuilder();
_connection = connection.WithUrl("https://localhost:44302/chathub").Build();
}
public async Task SendMessage(Msg model)
{
await _connection.StartAsync();
await _connection.SendAsync("Send", model);
}
}
由于我的 WebAPI 会多次调用 SignalR，我想在 WebAPI 和 SignalR 之间创建单一连接，而不是每次都关闭/打开连接。目前，我将 ChatApi 类创建为单例并在构造函数中初始化集线器连接。
如何在调用 await _connection.StartAsync(); 之前检查连接是否已启动？
使用:Microsoft.AspNetCore.SignalR.Client v1.0.0-preview1-final
请您参考如下方法:
Microsoft.AspNetCore.SignalR.Client v1.1.0+
HubConnection 上有一个State 属性。
public class ChatApi
{
private readonly HubConnection _connection;
public ChatApi()
{
_connection = new HubConnectionBuilder()
.WithUrl("https://localhost:44302/chathub")
.Build();
}
public async Task StartIfNeededAsync()
{
if (_connection.State == HubConnectionState.Disconnected)
{
await _connection.StartAsync();
}
}
public async Task SendMessage(Msg model)
{
await StartIfNeededAsync();
await _connection.SendAsync("Send", model);
}
}
引用资料:
- https://learn.microsoft.com/en-us/aspnet/core/signalr/dotnet-client
- aspnet/SignalR/pull/2204
- dotnet/aspnetcore@7625bbc
Microsoft.AspNetCore.SignalR.Client < v1.1.0
(在撰写本文时，最新版本为 1.0.0-preview2-final。)
没有 ConnectionState 属性。
您需要自己跟踪状态，方法是订阅 HubConnection 上的 Closed 事件。
public class ChatApi
{
private readonly HubConnection _connection;
private ConnectionState _connectionState = ConnectionState.Disconnected;
public ChatApi()
{
var connection = new HubConnectionBuilder();
_connection = connection.WithUrl("https://localhost:44302/chathub").Build();
// Subscribe to event
_connection.Closed += (ex) =>
{
if (ex == null)
{
Trace.WriteLine("Connection terminated");
_connectionState = ConnectionState.Disconnected;
}
else
{
Trace.WriteLine($"Connection terminated with error: {ex.GetType()}: {ex.Message}");
_connectionState = ConnectionState.Faulted;
}
};
}
public async Task StartIfNeededAsync()
{
if (_connectionState == ConnectionState.Connected)
{
return;
}
try
{
await _connection.StartAsync();
_connectionState = ConnectionState.Connected;
}
catch (Exception ex)
{
Trace.WriteLine($"Connection.Start Failed: {ex.GetType()}: {ex.Message}");
_connectionState = ConnectionState.Faulted;
throw;
}
}
private enum ConnectionState
{
Connected,
Disconnected,
Faulted
}
}
用法:
public async Task SendMessage(Msg model)
{
await StartIfNeededAsync();
await _connection.SendAsync("Send", model);
}
引用资料:
