我一直在研究一个示例，该示例在自托管WPF服务器应用程序中使用SignalR 2与WPF客户端进行通信。我已经下载了该项目-在下面显示该项目-一切正常：
WPF服务器：
public partial class MainWindow : Window
{
public IDisposable SignalR { get; set; }
const string ServerURI = "http://localhost:8080";
public MainWindow()
{
InitializeComponent();
}
/// <summary>
/// Calls the StartServer method with Task.Run to not
/// block the UI thread.
/// </summary>
private void ButtonStart_Click(object sender, RoutedEventArgs e)
{
WriteToConsole("Starting server...");
ButtonStart.IsEnabled = false;
Task.Run(() => StartServer());
}
/// <summary>
/// Stops the server and closes the form. Restart functionality omitted
/// for clarity.
/// </summary>
private void ButtonStop_Click(object sender, RoutedEventArgs e)
{
SignalR.Dispose();
Close();
}
/// <summary>
/// Starts the server and checks for error thrown when another server is already
/// running. This method is called asynchronously from Button_Start.
/// </summary>
private void StartServer()
{
try
{
SignalR = WebApp.Start(ServerURI);
}
catch (TargetInvocationException)
{
WriteToConsole("A server is already running at " + ServerURI);
this.Dispatcher.Invoke(() => ButtonStart.IsEnabled = true);
return;
}
this.Dispatcher.Invoke(() => ButtonStop.IsEnabled = true);
WriteToConsole("Server started at " + ServerURI);
}
///This method adds a line to the RichTextBoxConsole control, using Dispatcher.Invoke if used
/// from a SignalR hub thread rather than the UI thread.
public void WriteToConsole(String message)
{
if (!(RichTextBoxConsole.CheckAccess()))
{
this.Dispatcher.Invoke(() =>
WriteToConsole(message)
);
return;
}
RichTextBoxConsole.AppendText(message + "\r");
}
}
/// <summary>
/// Used by OWIN's startup process.
/// </summary>
class Startup
{
public void Configuration(IAppBuilder app)
{
app.UseCors(CorsOptions.AllowAll);
app.MapSignalR();
}
}
/// <summary>
/// Echoes messages sent using the Send message by calling the
/// addMessage method on the client. Also reports to the console
/// when clients connect and disconnect.
/// </summary>
public class MyHub : Hub
{
public void Send(string name, string message)
{
Clients.All.addMessage(name, message);
}
public override Task OnConnected()
{
//Use Application.Current.Dispatcher to access UI thread from outside the MainWindow class
Application.Current.Dispatcher.Invoke(() =>
((MainWindow)Application.Current.MainWindow).WriteToConsole("Client connected: " + Context.ConnectionId));
return base.OnConnected();
}
public override Task OnDisconnected()
{
//Use Application.Current.Dispatcher to access UI thread from outside the MainWindow class
Application.Current.Dispatcher.Invoke(() =>
((MainWindow)Application.Current.MainWindow).WriteToConsole("Client disconnected: " + Context.ConnectionId));
return base.OnDisconnected();
}
}
这是WPF客户端：
public partial class MainWindow : Window
{
/// <summary>
/// This name is simply added to sent messages to identify the user; this
/// sample does not include authentication.
/// </summary>
public String UserName { get; set; }
public IHubProxy HubProxy { get; set; }
const string ServerURI = "http://localhost:8080/signalr";
public HubConnection Connection { get; set; }
public MainWindow()
{
InitializeComponent();
}
private void ButtonSend_Click(object sender, RoutedEventArgs e)
{
HubProxy.Invoke("Send", UserName, TextBoxMessage.Text);
TextBoxMessage.Text = String.Empty;
TextBoxMessage.Focus();
}
/// <summary>
/// Creates and connects the hub connection and hub proxy. This method
/// is called asynchronously from SignInButton_Click.
/// </summary>
private async void ConnectAsync()
{
Connection = new HubConnection(ServerURI);
Connection.Closed += Connection_Closed;
HubProxy = Connection.CreateHubProxy("MyHub");
//Handle incoming event from server: use Invoke to write to console from SignalR's thread
HubProxy.On<string, string>("AddMessage", (name, message) =>
this.Dispatcher.Invoke(() =>
RichTextBoxConsole.AppendText(String.Format("{0}: {1}\r", name, message))
)
);
try
{
await Connection.Start();
}
catch (HttpRequestException)
{
StatusText.Content = "Unable to connect to server: Start server before connecting clients.";
//No connection: Don't enable Send button or show chat UI
return;
}
//Show chat UI; hide login UI
SignInPanel.Visibility = Visibility.Collapsed;
ChatPanel.Visibility = Visibility.Visible;
ButtonSend.IsEnabled = true;
TextBoxMessage.Focus();
RichTextBoxConsole.AppendText("Connected to server at " + ServerURI + "\r");
}
/// <summary>
/// If the server is stopped, the connection will time out after 30 seconds (default), and the
/// Closed event will fire.
/// </summary>
void Connection_Closed()
{
//Hide chat UI; show login UI
var dispatcher = Application.Current.Dispatcher;
dispatcher.Invoke(() => ChatPanel.Visibility = Visibility.Collapsed);
dispatcher.Invoke(() => ButtonSend.IsEnabled = false);
dispatcher.Invoke(() => StatusText.Content = "You have been disconnected.");
dispatcher.Invoke(() => SignInPanel.Visibility = Visibility.Visible);
}
private void SignInButton_Click(object sender, RoutedEventArgs e)
{
UserName = UserNameTextBox.Text;
//Connect to server (use async method to avoid blocking UI thread)
if (!String.IsNullOrEmpty(UserName))
{
StatusText.Visibility = Visibility.Visible;
StatusText.Content = "Connecting to server...";
ConnectAsync();
}
}
private void WPFClient_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
if (Connection != null)
{
Connection.Stop();
Connection.Dispose();
}
}
}
让我感到困惑的是服务器MyHub类中的“发送”方法，该方法将文本推送到所有连接的客户端。在该方法中，似乎在所有客户端上都调用了一个名为“ addMessage（String，String）”的方法，但是该方法未在客户端代码中的任何地方声明。这是怎么回事？
答案 0 :(得分：0)
在客户端代码中通过以下方式声明addMessage（String，String）方法：
HubProxy.On<string, string>("AddMessage", (name, message) =>
this.Dispatcher.Invoke(() =>
RichTextBoxConsole.AppendText(String.Format("{0}: {1}\r", name, message))
)
);
按照https://docs.microsoft.com/en-us/previous-versions/aspnet/jj917974%28v%3dvs.100%29
该方法是如下操作委托：
https://docs.microsoft.com/en-us/dotnet/api/system.action-2?&view=netframework-4.8