如何从FormFlow调用对话框

[Serializable]
public class MyForm
{
    [Prompt("请输入您的姓名：")]
    public string Name { get; set; }

    [Prompt("请输入您的年龄：")]
    public int Age { get; set; }

    public static IForm<MyForm> BuildForm()
    {
        return new FormBuilder<MyForm>()
            .Message("欢迎使用对话框！")
            .Build();
    }
}

public class MyDialog : IDialog<object>
{
    public async Task StartAsync(IDialogContext context)
    {
        var myFormDialog = FormDialog.FromForm(MyForm.BuildForm, FormOptions.PromptInStart);
        context.Call(myFormDialog, this.ResumeAfterFormDialog);
    }

    private async Task ResumeAfterFormDialog(IDialogContext context, IAwaitable<MyForm> result)
    {
        try
        {
            var form = await result;
            // 在这里可以处理对话框的结果
            await context.PostAsync($"您的姓名是：{form.Name}，年龄是：{form.Age}。");
        }
        catch (FormCanceledException ex)
        {
            await context.PostAsync($"对话框已取消：{ex.Message}");
        }
        finally
        {
            context.Done<object>(null);
        }
    }
}

public class RootDialog : IDialog<object>
{
    public async Task StartAsync(IDialogContext context)
    {
        context.Wait(this.MessageReceivedAsync);
    }

    private async Task MessageReceivedAsync(IDialogContext context, IAwaitable<IMessageActivity> result)
    {
        var message = await result;
        if (message.Text.ToLower().Contains("调用对话框"))
        {
            // 调用对话框
            context.Call(new MyDialog(), this.ResumeAfterDialog);
        }
        else
        {
            await context.PostAsync("请输入“调用对话框”以调用对话框。");
            context.Wait(this.MessageReceivedAsync);
        }
    }

    private async Task ResumeAfterDialog(IDialogContext context, IAwaitable<object> result)
    {
        // 对话框完成后的处理
        context.Wait(this.MessageReceivedAsync);
    }
}

public class MessagesController : ApiController
{
    private static readonly IDialog<object> RootDialog = new RootDialog();

    public async Task<HttpResponseMessage> Post([FromBody]Activity activity)
    {
        if (activity.Type == ActivityTypes.Message)
        {
            await Conversation.SendAsync(activity, () => RootDialog);
        }
        else
        {
            HandleSystemMessage(activity);
        }
        var response = Request.CreateResponse(HttpStatusCode.OK);
        return response;
    }

    private Activity HandleSystemMessage(Activity message)
    {
        // 处理系统消息
        return null;
    }
}