/// <summary>
/// If no canExecute deletage is provided, CanExecute allows a single simultaneous command execution
/// </summary>
/// <param name="parameter">Ignored; this is the paremeterless command class</param>
/// <returns></returns>
public bool CanExecute(object parameter = null)
{
try
{
return(canExecute != null?canExecute() : executingCount == 0);
}
catch (Exception ex)
{
XLog.Trace(ex);
return(true);
}
}
// Asynchronous command handling based on http://stackoverflow.com/a/31595509/6043538
public async void Execute(object?parameter = null)
{
var couldExecuteBeforeExecute = CanExecute();
if (!couldExecuteBeforeExecute)
{
return;
}
Interlocked.Increment(ref executingCount);
var couldExecuteDuringExecute = CanExecute();
if (couldExecuteDuringExecute != couldExecuteBeforeExecute)
{
RaiseCanExecuteChanged(); // TODO: test if always raising canexecutechanged does not disturb normal UI element update during a short synchronous command. If so, keep preventing multiple execution but only raise CanExecuteChanged for asynchrounous commands
}
try
{
if (execute != null)
{
execute();
}
else if (asyncExecute != null)
{
await asyncExecute();
}
else
{
throw new Exception("Execute is null");
}
}
catch (Exception ex)
{
XLog.Trace(ex);
}
finally
{
Interlocked.Decrement(ref executingCount);
var couldExecuteAfterExecute = CanExecute();
if (couldExecuteAfterExecute != couldExecuteDuringExecute)
{
RaiseCanExecuteChanged();
}
}
}