Aufgabe Timer in Titel

FahzeugWPF/MainWindow.xaml

@@ -6,7 +6,7 @@
         xmlns:local="clr-namespace:FahzeugWPF"
         mc:Ignorable="d"
         d:DataContext="{d:DesignInstance Type=local:MainWindowViewModel, IsDesignTimeCreatable=False}"
-        Title="Fahrzeuge" Height="450" Width="800">
+        Title="{Binding Path=MainWindowTitle}" Height="450" Width="800">
     <StackPanel>
         <DataGrid Name="dgTest"
                   CanUserAddRows="False"

FahzeugWPF/MainWindowViewModel.cs

@@ -1,18 +1,30 @@
 using FahrzeugDatenBank;
 using System.Collections.ObjectModel;
+using System.Timers;
 
 namespace FahzeugWPF;
 
-class MainWindowViewModel
+class MainWindowViewModel : ViewModelBase
 {
     private readonly FahrzeugeModell _model;
+    private string _mainWindowTitle = "Fahrzeuge";
+    private System.Timers.Timer _timer = new System.Timers.Timer()
+    {
+        Interval = 1000,
+    };
 
     public MainWindowViewModel(FahrzeugeModell modell)
     {
+        this._timer.Elapsed += _timer_Elapsed;
+        this._timer.Start();
         this._model = modell;
         this.InitialisiereDasViewModell();
     }
 
+    public string MainWindowTitle { get { return _mainWindowTitle; } set {
+            SetProperty<string>(ref _mainWindowTitle, value);
+        } }
+
     public ObservableCollection<Fahrzeug> Fahrzeuge { get; } = new ObservableCollection<Fahrzeug>();
 
     private async void InitialisiereDasViewModell()
@@ -23,4 +35,9 @@ class MainWindowViewModel
             this.Fahrzeuge.Add(fahrzeug);
         }
     }
+
+    private void _timer_Elapsed(object? sender, ElapsedEventArgs e)
+    {
+        this.MainWindowTitle = $"Fahrzeuge {DateTime.Now.ToLongTimeString()}";
+    }
 }

FahzeugWPF/RelayCommand.cs

@@ -0,0 +1,44 @@
+namespace FahzeugWPF;
+
+using System.Diagnostics;
+using System.Windows.Input;
+
+public class RelayCommand : ICommand
+{
+    readonly Action<object> _execute = null;
+    readonly Predicate<object> _canExecute = null;
+
+    public RelayCommand(Action<object> execute)
+        : this(execute, null)
+    {
+        // Nothing to do
+    }
+
+    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
+    {
+        if (execute == null)
+        {
+            throw new ArgumentNullException("execute");
+        }
+
+        this._execute = execute;
+        this._canExecute = canExecute;
+    }
+
+    [DebuggerStepThrough]
+    public bool CanExecute(object parameter)
+    {
+        return _canExecute == null ? true : _canExecute(parameter);
+    }
+
+    public event EventHandler CanExecuteChanged
+    {
+        add { CommandManager.RequerySuggested += value; }
+        remove { CommandManager.RequerySuggested -= value; }
+    }
+
+    public void Execute(object parameter)
+    {
+        _execute(parameter);
+    }
+}

FahzeugWPF/ViewModelBase.cs

@@ -0,0 +1,60 @@
+namespace FahzeugWPF;
+
+using System.ComponentModel;
+using System.Linq.Expressions;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+public abstract class ViewModelBase : INotifyPropertyChanged
+{
+    #region Events
+
+    [field: NonSerialized]
+    public event PropertyChangedEventHandler PropertyChanged;
+
+    protected void OnPropertyChanged(Expression<Func<object>> expression)
+    {
+        var lambdaExpression = expression as LambdaExpression;
+
+        MemberExpression memberExpression = null;
+        if (lambdaExpression.Body is UnaryExpression)
+        {
+            var unaryExpression = lambdaExpression.Body as UnaryExpression;
+            memberExpression = unaryExpression.Operand as MemberExpression;
+        }
+        else
+        {
+            memberExpression = lambdaExpression.Body as MemberExpression;
+        }
+
+        if (memberExpression != null)
+        {
+            var propertyInfo = memberExpression.Member as PropertyInfo;
+            if (propertyInfo != null)
+            {
+                OnPropertyChanged(propertyInfo.Name);
+            }
+        }
+    }
+
+    protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
+    {
+        if (PropertyChanged != null)
+        {
+            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+        }
+    }
+
+    protected bool SetProperty<T>(ref T field, T value, [CallerMemberName] string? propertyName = null)
+    {
+        if (EqualityComparer<T>.Default.Equals(field, value))
+        {
+            return false;
+        }
+
+        field = value;
+        OnPropertyChanged(propertyName);
+        return true;
+    }
+    #endregion Events
+}