I am new to the BotFramework v4 coming from v3, having a hard time understanding the dialog concept of v4

I am trying to ask the user for example his age and then I want to end the conversation I tried to dynamically add the dialog to the `DialogSet` but both `ContinueDialogAsync` and `ResumeDialogAsync` will not get called. The conversations ends right after the prompt and the answer will not be awaited.

Here is the call of the TextPrompt:

```
dialogContext.Dialogs.Add(new TextPrompt("age"));
return await dialogContext.PromptAsync("age", new PromptOptions
{
    Prompt = MessageFactory.Text("How old are you?")
});

```

Do I really need to implement a WaterfallDialog with a single step to achieve this?