Simple MVVM binding issue - wpf

Question

I have one textbox and one button. The Button Command should change the property which is binded to the TextBox.
But I don't see any visual changes after command execution.
I think it easy question related to wpf binding
Please help me with this issue
Source of app:
<UserControl.DataContext>
<local:SampleViewModel />
</UserControl.DataContext>
<Grid>
<StackPanel>
<TextBox Height="23" Width="120" Text="{Binding MyName}" />
<Button Content="Click" Command="{Binding ButtonCommand}" />
</StackPanel>
</Grid>
ViewModel:
Private _myName As String
Public Property MyName As String
Get
Return _myName
End Get
Set(value As String)
_myName = value
OnPropertyChanged("MyName")
End Set
End Property
Public _buttonCommand As DelegateCommand
Public ReadOnly Property ButtonCommand As DelegateCommand
Get
Return If(_buttonCommand IsNot Nothing, _buttonCommand,
New DelegateCommand(AddressOf Execute, AddressOf CanExecute))
End Get
End Property
Private Sub Execute()
MyName = "Executed"
End Sub
Private Function CanExecute() As Boolean
Return True
End Function
Public Event PropertyChanged As PropertyChangedEventHandler
Private Sub OnPropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub

Answer 1

Do the following:
1.
Class MainWindow
Implements INotifyPropertyChanged
2 . In Public Sub New() make sure you write Me.DataContext = Me to set the DataContext
Note: Ignore step 2 if you're using a ViewModel and setting it in XAML
3 . Modify the ProperyChanged like this:
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Only after implementing INotifyPropertyChanged correctly will the Binding correctly refresh the MyName property after the PropertyChanged event

Answer 2

Here is a code that works with your exact XAML (I took the DelegateCommand implementation from http://wpftutorial.net/DelegateCommand.html ) Sorry it's C#, i'm really not into VB :D
public class DelegateCommand : ICommand
{
private readonly Predicate<object> _canExecute;
private readonly Action<object> _execute;
public event EventHandler CanExecuteChanged;
public DelegateCommand(Action<object> execute)
: this(execute, null)
{
}
public DelegateCommand(Action<object> execute,
Predicate<object> canExecute)
{
_execute = execute;
_canExecute = canExecute;
}
public virtual bool CanExecute(object parameter)
{
if (_canExecute == null)
{
return true;
}
return _canExecute(parameter);
}
public virtual void Execute(object parameter)
{
_execute(parameter);
}
public void RaiseCanExecuteChanged()
{
if (CanExecuteChanged != null)
{
CanExecuteChanged(this, EventArgs.Empty);
}
}
}
public class SampleViewModel : INotifyPropertyChanged
{
// Create the OnPropertyChanged method to raise the event
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
public event PropertyChangedEventHandler PropertyChanged;
public DelegateCommand _buttonCommand;
public DelegateCommand ButtonCommand
{
get
{
if (_buttonCommand == null)
{
_buttonCommand = new DelegateCommand(Execute);
}
return _buttonCommand;
}
}
public void Execute(object o)
{
MyName = "executed";
}
public string MyName { get { return _myName; } set { _myName = value; OnPropertyChanged("MyName"); } }
private string _myName;
}