implemented ConnectionRequestEventArgs to provide Connection result (Sucess or failure) to ProtocolSettingsViewModel

MultiTerm.Core/ViewModel/TerminalViewModel.cs

@@ -26,13 +26,12 @@ public abstract partial class TerminalViewModel : ObservableObject, ITerminalVie
             // register event handler for connection request from viewmodel
             if(value != null)
             {
-                protocolSettings!.ConnectRequested += OnViewModelRequestedConnect; ;
+                protocolSettings!.ConnectRequested += OnViewModelRequestedConnect; ; ;
                 protocolSettings!.DisconnectRequested += OnViewModelRequestedDisconnect;
             }
         }
     }
 
-
     /// <summary>
     /// Method to override if any closing actions are required.
     /// Closing can be cancelled using the return value.
@@ -49,13 +48,19 @@ public abstract partial class TerminalViewModel : ObservableObject, ITerminalVie
         }
     }
 
-    private void OnViewModelRequestedConnect(object? sender, IProtocolSettings e)
+    private void OnViewModelRequestedConnect(object? sender, ConnectionRequestEventArgs e)
     {
-        this.CommunicationProtocol?.Connect(e);
+        // guard uninitialized CommunicationProtocol
+        if (CommunicationProtocol == null) { throw new Exception($"To call '{nameof(OnViewModelRequestedConnect)}()', CommunicationProtocol must not be null!"); }
+
+        e.Success = this.CommunicationProtocol.Connect(e.Settings);
     }
 
     private void OnViewModelRequestedDisconnect(object? sender, EventArgs e)
     {
-        this.CommunicationProtocol?.Disconnect();
+        // guard uninitialized CommunicationProtocol
+        if (CommunicationProtocol == null) { throw new Exception($"To call '{nameof(OnViewModelRequestedConnect)}()', CommunicationProtocol must not be null!"); }
+
+        this.CommunicationProtocol.Disconnect();
     }
 }

MultiTerm.Protocols/CommunicationProtocol.cs

@@ -59,13 +59,13 @@ public abstract class CommunicationProtocol : ICommunicationProtocol
     /// <param name="ct">cancellation token</param>
     protected abstract void InternalRead(CancellationToken ct);
 
-    public void Connect(IProtocolSettings settings)
+    public bool Connect(IProtocolSettings settings)
     {
         // check if settings are valid, cancel if not
         if (settings.AreValid() == false)
         {
             this.logger.LogError($"'{nameof(Connect)}()' failed since the provided protocol settings are invalid", nameof(CommunicationProtocol));
-            return;
+            return false;
         }
 
         // try connecting if serttings are valid
@@ -76,10 +76,12 @@ public abstract class CommunicationProtocol : ICommunicationProtocol
             // start internal reading thread
             this.readingThread = new Thread(() => this.InternalRead(this.cancellationTokenSource.Token));
             this.readingThread.Start();
+            return true;
         }
         else
         {
             this.logger.LogWarn($"'{nameof(Connect)}()' failed to connect to protocol, did not start reading thread.", nameof(CommunicationProtocol));
+            return false;
         }
     }
 

MultiTerm.Protocols/ConnectionRequestEventArgs.cs

@@ -0,0 +1,25 @@
+namespace MultiTerm.Protocols;
+
+public class ConnectionRequestEventArgs : EventArgs
+{
+    /// <summary>
+    /// Settings object, contains all settings that are required to connect.
+    /// </summary>
+    public IProtocolSettings Settings { get; private set; }
+
+    /// <summary>
+    /// Indicates wether the connection could be successfully made.
+    /// </summary>
+    public bool Success { get; set; }
+
+    /// <summary>
+    /// Creates instance of event args with given <paramref name="settings"/>.
+    /// Defaults <see cref="Success"/> to <see cref="true"/>.
+    /// </summary>
+    /// <param name="settings">settings object</param>
+    public ConnectionRequestEventArgs(IProtocolSettings settings)
+    {
+        this.Settings = settings;
+        this.Success = true;
+    }
+}

MultiTerm.Protocols/ICommunicationProtocol.cs

@@ -26,7 +26,7 @@ public interface ICommunicationProtocol
     /// Connect to the device.
     /// </summary>
     /// <param name="settings">settings required to connect and use the protocol</param>
-    void Connect(IProtocolSettings settings);
+    bool Connect(IProtocolSettings settings);
 
     /// <summary>
     /// Disconnect from the device. Ends all internal activities.

MultiTerm.Protocols/IProtocolSettingsViewModel.cs

@@ -13,7 +13,7 @@ public interface IProtocolSettingsViewModel
     /// Event that is thrown when the user requested to connect to the device with the entered settings.
     /// Provides protocol settings to use for connection.
     /// </summary>
-    event EventHandler<IProtocolSettings> ConnectRequested;
+    event EventHandler<ConnectionRequestEventArgs> ConnectRequested;
 
     /// <summary>
     /// Event that is thrown when the user requested to disconnect from the device.

MultiTerm.Protocols/ProtocolSettingsViewModel.cs

@@ -16,7 +16,7 @@ public abstract partial class ProtocolSettingsViewModel : ObservableObject, IPro
     private const string disconnectedStateButtonText = "Connect";
     protected readonly IMessenger messenger;
 
-    public event EventHandler<IProtocolSettings>? ConnectRequested;
+    public event EventHandler<ConnectionRequestEventArgs>? ConnectRequested;
     public event EventHandler? DisconnectRequested;
 
     public abstract ProtocolType ProtocolType { get; }
@@ -50,9 +50,24 @@ public abstract partial class ProtocolSettingsViewModel : ObservableObject, IPro
             {
                 // CONNECT
                 this.AreEditable = false;
-                this.ConnectRequested?.Invoke(this, (IProtocolSettings)this);  // implementing class must also implement IProtocolSettings!
+
+                // create event args. Important: derivative classes must also implement IProtocolSettings!
+                var eventArgs = new ConnectionRequestEventArgs((IProtocolSettings)this);
+                // fire event
+                this.ConnectRequested?.Invoke(this, eventArgs);
+
+                // after invoke: connection was made successfully?
+                if (eventArgs.Success)
+                {
+                    // set button to connected state
                     this.ConnectDisconnectButtonText = connectedStateButtonText;
                 }
+                else
+                {
+                    // rollback
+                    this.AreEditable = true;
+                }
+            }
             // if currently connected
             else if (this.ConnectDisconnectButtonText == connectedStateButtonText)
             {