WPF Custom commands changing a picture

Question

I am attempting to change a picture when clicking on it in the sidebar menu, but however nothing seem to happen when I click on a image. This is done in WPF and for a image editing program. I have been reading up on custom commands and reading other custom commands posts here on StackOverflow but I can't seem to find anything that apply to this case.

public partial class ImageEditor : UserControl
{
    ICommand changePicture;
    public ICommand ChangePicture 
    { 
        get { return changePicture; }
        set { changePicture = value; } 
    }

    public ImageEditor()
    {
        InitializeComponent();
    }

    public void loadImages(string _imageFile)
    {
        string directory = Path.GetDirectoryName(_imageFile);
        string[] _filePaths = Directory.GetFiles(directory, "*.jpg");
        foreach (string image in _filePaths)
        {
            if (image.Length > 0)
            {
                thumbNails.Children.Add(addPictureButton(image));
            }
        }
    }

    public Button addPictureButton(string image)
    {
        Image currentImage = new Image();
        currentImage.Source = new BitmapImage(new Uri(image));
        currentImage.Stretch = Stretch.Fill;

        Grid grid = new Grid();
        grid.Height = 90;
        grid.Children.Add(currentImage);

        var newButton = new MyButton();
        newButton.Content = grid;
        newButton.Name = "button";
        newButton.Height = 100;
        newButton.Background = Brushes.Chocolate;
        newButton.ImageRef = image;
        newButton.Command = ChangePicture;
        return newButton;
    }
}

I think there is a problem with my custom command, this is the main method where I load all the pictures.

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    /// Get the Handle for the Forms System Menu
    IntPtr systemMenuHandle = GetSystemMenu(this.Handle, false);
    /// Create our new System Menu items just before the Close menu item
    InsertMenu(systemMenuHandle, 5, MF_BYPOSITION | MF_SEPARATOR, 0, string.Empty); // <-- Add a menu seperator
    InsertMenu(systemMenuHandle, 6, MF_BYPOSITION, _SettingsSysMenuID, "Inställningar...");
    InsertMenu(systemMenuHandle, 7, MF_BYPOSITION, _CalibrateSysMenuID, "Kalibrerings Läge (På/Av)");
    InsertMenu(systemMenuHandle, 8, MF_BYPOSITION, _ZoomPrevSysMenuID, "Zoom Läge -1");
    InsertMenu(systemMenuHandle, 9, MF_BYPOSITION, _ZoomNextSysMenuID, "Zoom Läge +1");
    //InsertMenu(systemMenuHandle, 10, MF_BYPOSITION, _PrintSysMenuID, "Print...");

    // Attach our WndProc handler to this Window
    HwndSource source = HwndSource.FromHwnd(this.Handle);
    source.AddHook(new HwndSourceHook(WndProc));

    if (ImageFile != null && ImageFile.Length > 0)
    {
        if (_cameraManager != null)
            _cameraManager.IsPaused = true;

        Bitmap bitmap = new Bitmap(ImageFile);
        UcImageGrabbedControls.SetImageToView(bitmap);
        ImagePicker.loadImages(ImageFile);
        ImagePicker.ChangePicture = new CustomCommand(OnPictureClick);

        BtnGrab.IsToggled = true;

        UpdateShownControls();
    }
}

Button goes here

public void OnPictureClick(object sender)
{
    var button = (UserControls.MyButton)sender;
    if (button == null)
        return;

    var bitmap = new Bitmap(button.ImageRef);
    UcImageGrabbedControls.SetImageToView(bitmap);
}

Custom command implementation

public class CustomCommand : ICommand
{
    //public delegate void ExecutedMethod();
    //private ExecutedMethod method;
    private Action<object> onPictureClick;

    public CustomCommand(/*ExecutedMethod executed*/)
    {
        //method = executed;
    }

    public CustomCommand(Action<object> onPictureClick)
    {
        this.onPictureClick = onPictureClick;
    }

    public event EventHandler CanExecuteChanged;

    public bool CanExecute(object parameter)
    {
        return true;
    }

    public void Execute(object parameter)
    {
        //method();
    }
}

Answer 1

This class looks like a lot of people tinkered with it until it broke, so I removed everything that is no longer in use anyway.

public class CustomCommand : ICommand
{
    private Action<object> onPictureClick;

    public CustomCommand(Action<object> onPictureClick)
    {
        this.onPictureClick = onPictureClick;
    }

    public event EventHandler CanExecuteChanged;

    public bool CanExecute(object parameter)
    {
        return true;
    }

    public void Execute(object parameter)
    {
        // Nothing happening here :(
    }
}

The basic problem is, that the Execute method doesn't do anything - unsurprisingly any button executing this command doesn't do anything either. The simplest fix would be to simply restore functionality to this method by invoking the method passed to the constructor:

public void Execute(object parameter)
{
    onPictureClick.Invoke(parameter);
    // or onPictureClick(parameter)
}

Since you are already working on that method, I suggest you rename the action to something less specific, e.g _action.

If you ever intend (or need) to make use of the CanExecute feature and/or use the CommandParameter I suggest you take a look at a RelayCommand implementation.
(This answer has a detailed explanation).