dc.BeginDialogAsync： "Value cannot be null.nParameter name: options"

Question

每次我运行await dc.BeginDialogAsync("sign-in");时，我都会得到这个没有意义的异常，因为其余参数都是可选的。这让我超级困惑。这是我的代码：

public FlexoBot(ConversationState conversationState)
{
    this.dialogState = conversationState.CreateProperty<DialogState>("dialog-state");
    this.dialogs = new DialogSet(this.dialogState);
    // Make oauth card available to use for all handlers
    this.dialogs.Add(new OAuthPrompt("oauth", new OAuthPromptSettings() { ConnectionName = "flexo-auth" }));
    dialogs.Add(new WaterfallDialog("sign-in", new WaterfallStep[] {
        PromptSignIn,
        GreetUser,
    }));
}

protected override async Task OnMembersAddedAsync(IList<ChannelAccount> membersAdded, ITurnContext<IConversationUpdateActivity> turnContext, CancellationToken cancellationToken)
{
    var dc = await this.dialogs.CreateContextAsync(turnContext);
    foreach (var member in membersAdded)
    {
        if (member.Id != turnContext.Activity.Recipient.Id)
        {
            await dc.BeginDialogAsync("sign-in");
            // Throws: System.ArgumentNullException has been thrown "Value cannot be null.nParameter name: options"
        }
    }
}

Answer 1

我终于想通了。这是因为我在瀑布台阶中呼唤return step.PromptAsync("oauth", null);。我把它改成：

return step.PromptAsync("oauth", new PromptOptions { });

它现在有效。