问Prompt.Choice中的重复评级

EN

private const string fiverate = "★★★★★";
private const string fourrate = "★★★★";
private const string threerate = "★★★";
private const string tworate = "★★";
private const string Onerate = "★";

public async Task ShowRating(IDialogContext context)
{
    PromptDialog.Choice(context,this.OnOptionRating, new List<string>() { fiverate,fourrate,threerate,tworate,Onerate }," "," ",3);          
}

private async Task OnOptionRating(IDialogContext context, IAwaitable<string> result)
{
    try
    {
        string optionSelected = await result;

        switch (optionSelected)
        {
            case fiverate:
                await context.PostAsync("Five Star");
                context.Done(String.Empty);
                break;
            case fourrate:
                await context.PostAsync("Four Star");
                context.Done(String.Empty);
                break;
            case threerate:
                await context.PostAsync("Three Star");
                context.Done(String.Empty);
                break;
            case tworate:
                await context.PostAsync("Two Star");
                context.Done(String.Empty);
                break;
            case Onerate:
                await context.PostAsync("One Star");
                context.Done(String.Empty);
                break;
        }
    }
    catch (TooManyAttemptsException ex)
    {
        await context.PostAsync($"Ooops! Too many attemps :(. But don't worry, I'm handling that exception and you can try again!");

        context.Wait(this.MessageReceivedAsync);
    }
}