Changing the cursor in WPF sometimes works, sometimes doesn't

Do you need the cursor to be a "wait" cursor only when it's over that particular page/usercontrol? If not, I'd suggest using Mouse.OverrideCursor:

Mouse.OverrideCursor = Cursors.Wait;try{    // do stuff}finally{    Mouse.OverrideCursor = null;}

This overrides the cursor for your application rather than just for a part of its UI, so the problem you're describing goes away.

One way we do this in our application is using IDisposable and then with using(){} blocks to ensure the cursor is reset when done.

public class OverrideCursor : IDisposable{  public OverrideCursor(Cursor changeToCursor)  {    Mouse.OverrideCursor = changeToCursor;  }  #region IDisposable Members  public void Dispose()  {    Mouse.OverrideCursor = null;  }  #endregion}

and then in your code:

using (OverrideCursor cursor = new OverrideCursor(Cursors.Wait)){  // Do work...}

The override will end when either: the end of the using statement is reached or; if an exception is thrown and control leaves the statement block before the end of the statement.

Update

To prevent the cursor flickering you can do:

public class OverrideCursor : IDisposable{  static Stack<Cursor> s_Stack = new Stack<Cursor>();  public OverrideCursor(Cursor changeToCursor)  {    s_Stack.Push(changeToCursor);    if (Mouse.OverrideCursor != changeToCursor)      Mouse.OverrideCursor = changeToCursor;  }  public void Dispose()  {    s_Stack.Pop();    Cursor cursor = s_Stack.Count > 0 ? s_Stack.Peek() : null;    if (cursor != Mouse.OverrideCursor)      Mouse.OverrideCursor = cursor;  }}

You can use a data trigger (with a view model) on the button to enable a wait cursor.

<Button x:Name="NextButton"        Content="Go"        Command="{Binding GoCommand }">    <Button.Style>         <Style TargetType="{x:Type Button}">             <Setter Property="Cursor" Value="Arrow"/>             <Style.Triggers>                 <DataTrigger Binding="{Binding Path=IsWorking}" Value="True">                     <Setter Property="Cursor" Value="Wait"/>                 </DataTrigger>             </Style.Triggers>         </Style>    </Button.Style></Button>

Here is the code from the view-model:

public class MainViewModel : ViewModelBase{   // most code removed for this example   public MainViewModel()   {      GoCommand = new DelegateCommand<object>(OnGoCommand, CanGoCommand);   }   // flag used by data binding trigger   private bool _isWorking = false;   public bool IsWorking   {      get { return _isWorking; }      set      {         _isWorking = value;         OnPropertyChanged("IsWorking");      }   }   // button click event gets processed here   public ICommand GoCommand { get; private set; }   private void OnGoCommand(object obj)   {      if ( _selectedCustomer != null )      {         // wait cursor ON         IsWorking = true;         _ds = OrdersManager.LoadToDataSet(_selectedCustomer.ID);         OnPropertyChanged("GridData");         // wait cursor off         IsWorking = false;      }   }}