In the Esri's ArcGIS for SharePoint SDK, you can create buttons in the SharePoint ribbon.  In this example, I will talk about the OnHidden event.  This event fires when the Hide() is called on the floating window after it is displayed.  This can be used to signal a process that the event is finished, and now you can do some other process or show another form etc...

Here I just implemented ICommand, and kept everything default.  I created a custom event EventHandler called OnHidden that will get call when the floating window is hidden or closed by a user.

    [Export(typeof(ICommand))]
    [DisplayNameAttribute("This is a Demo")]
    [DefaultIcon("/DemoFun;component/Images/Demo.png")]
    public class cmdGenerateExcelTemplate : ICommand
    {
        public bool CanExecute(object parameter)
        {
            return true;
        }

        public event EventHandler CanExecuteChanged;
        public event EventHandler OnHidden;
     
        public void Execute(object parameter)
        {
         
            MapApplication.Current.ShowWindow("This is my control",
                 <controlobject>,
                false,
                null,
                OnHidden,
                WindowType.Floating);
            this.OnHidden += new EventHandler(cmdGenerateExcelTemplate_OnHidden);

        }

        void cmdGenerateExcelTemplate_OnHidden(object sender, EventArgs e)
        {
            MessageBox.Show("I'm hidden now!");
        }
That's It.  It's very easy to do, and helpful in some instances.

Enjoy