ClientApiPoC/Shared/SignalR/TunnelClient.cs

using Microsoft.AspNetCore.SignalR.Client;

namespace ClientApiPoC.Shared.SignalR {
    public class TunnelClient : NotifyPropertyChangedBase, IDisposable, IAsyncDisposable {
        #region IDisposable-Implementierung
        private bool _disposed;

        protected virtual void Dispose(bool disposing) {
            if (!_disposed) {
                if (disposing) {
                    _ = this.DisposeAsync();
                }
                _disposed = true;
            }
        }

        public void Dispose() {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        public async ValueTask DisposeAsync() {
            await DisconnectAsync();
        }
        #endregion

        private HubConnection? _connection = null;

        public bool IsConnected => (this.ConnectionState == HubConnectionState.Connected);

        public bool IsConnecting => (this.ConnectionState == HubConnectionState.Connecting || this.ConnectionState == HubConnectionState.Reconnecting);

        protected HubConnectionState ConnectionState => (_connection?.State ?? HubConnectionState.Disconnected);

        public async Task ConnectAsync(string url, Action<HubConnection> configureConnection) {
            try {
                if (string.IsNullOrWhiteSpace(url)) throw new ArgumentNullException(nameof(url));
                if (this.IsConnected) throw new InvalidOperationException("SignalR connection is already established.");
                _connection = new HubConnectionBuilder().WithUrl(url).WithAutomaticReconnect().Build();
                _connection.Reconnecting += Connection_Reconnecting;
                _connection.Reconnected += Connection_Reconnected;
                _connection.Closed += Connection_Closed;
                configureConnection(_connection);
                await _connection.StartAsync();
            } finally {
                await UpdateStateAsync();
            }
        }

        public async Task DisconnectAsync() {
            try {
                if (_connection == null) return;
                try {
                    if (this.IsConnected) await _connection.StopAsync();
                } catch { }
                _connection.Reconnecting -= Connection_Reconnecting;
                _connection.Reconnected -= Connection_Reconnected;
                _connection.Closed -= Connection_Closed;
                await _connection.DisposeAsync();
                _connection = null;
            } finally {
                await UpdateStateAsync();
            }
        }

        private async Task Connection_Reconnecting(Exception? arg) {
            await UpdateStateAsync();
        }

        private async Task Connection_Reconnected(string? arg) {
            await UpdateStateAsync();
        }

        private async Task Connection_Closed(Exception? arg) {
            await UpdateStateAsync();
        }

        private async Task UpdateStateAsync() {
            OnPropertyChanged(nameof(IsConnected));
            OnPropertyChanged(nameof(IsConnecting));
            await Task.CompletedTask;
        }
    }
}