public DialogStep(Func<string, Task<DialogStepResult>> textProcessingAction, Func<IRandomAccessStream, Task<DialogStepResult>> imageProcessingAction)
{
Check.Required<ArgumentNullException>(() => textProcessingAction != null);
Check.Required<ArgumentNullException>(() => textProcessingAction != null);
_textProcessingAction = textProcessingAction;
_imageProcessAction = imageProcessingAction;
}