Error: Stack is empty exception in Bot Framework

Hi,

I created a chatbot by Bot Framework and I implemented a Reset option in order to delete the conversation e grant to the user to begin a new conversation.

// MessageController.cs
public async Task Post([FromBody]Activity activity)
{
await Conversation.SendAsync(activity, () => new RootDialog().DefaultIfException());
return Request.CreateResponse(HttpStatusCode.OK); <- Stack is empty Exception
}
// RootDialog.cs

private void ShowMenuOptions(IDialogContext context)
{
List<string> optionList = new List<string>();
optionList.Add("Info");
optionList.Add("Support");
optionList.Add("Reset");
string prompt ="How can I help you?";
PromptDialog.Choice(context, this.OnOptionSelected, (IEnumerable<string>)optionList, prompt, retry, attempts);
}
private async Task OnOptionSelected(IDialogContext context, IAwaitable<string> result)
{
try
{
string optionSelected = await result;
switch (optionSelected)
{
case "Reset":
context.Reset();
context.ConversationData.Clear();
context.PrivateConversationData.Clear();
context.UserData.Clear();
break;
}
}
}

When an user chooses reset option, the bot answers with "Sorry, my bot code is having an issue."

Debugging the code I see that the exception triggers after context.Reset().

Can anybody help me and solve it?

I solved it implementing global Reset message handler.

First of all I created a new CancelScorable

public class CancelScorable : ScorableBasestring, double>
{
private readonly IDialogTask task;
private readonly IBotData botData;
public CancelScorable(IDialogTask task, IBotData botData)
{
SetField.NotNull(out this.task, nameof(task), task);
SetField.NotNull(out this.botData, nameof(botData), botData);
}
protected override async Task<string> PrepareAsync(IActivity activity, CancellationToken token)
{
var message = activity as IMessageActivity;
if (message != null && !string.IsNullOrWhiteSpace(message.Text))
{
if (message.Text.Equals("reset", StringComparison.InvariantCultureIgnoreCase))
{
return message.Text;
}
}
return null;
}
protected override bool HasScore(IActivity item, string state)
{
return state != null;
}
protected override double GetScore(IActivity item, string state)
{
return 1.0;
}
protected override async Task PostAsync(IActivity item, string state, CancellationToken token)
{
this.task.Reset();
botData.UserData.Clear();
botData.PrivateConversationData.Clear();
await botData.FlushAsync(token);
}
protected override Task DoneAsync(IActivity item, string state, CancellationToken token)
{
return Task.CompletedTask;
}
}

Then I create GlobalMessageHandlersBotModule

public class GlobalMessageHandlersBotModule : Module
{
protected override void Load(ContainerBuilder builder)
{
base.Load(builder);
builder
.Register(c => new CancelScorable(c.Resolve(), c.Resolve()))
.Asdouble>>()
.InstancePerLifetimeScope();
}
}

At last I registried in GlobalAsax

protected void Application_Start()
{
this.RegisterBotModules();
GlobalConfiguration.Configure(WebApiConfig.Register);
}
private void RegisterBotModules()
{
var builder = new ContainerBuilder();
builder.RegisterModule(new ReflectionSurrogateModule());
builder.RegisterModule();
builder.Update(Conversation.Container);
}

I hope this can help you!

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Emanuele Leoni8y ago
I solved it implementing global Reset message handler.
First of all I created a new CancelScorable
public class CancelScorable : ScorableBasestring, double>
{
private readonly IDialogTask task;
private readonly IBotData botData;

public CancelScorable(IDialogTask task, IBotData botData)
{
SetField.NotNull(out this.task, nameof(task), task);
SetField.NotNull(out this.botData, nameof(botData), botData);
}

protected override async Task<string> PrepareAsync(IActivity activity, CancellationToken token)
{
var message = activity as IMessageActivity;

if (message != null && !string.IsNullOrWhiteSpace(message.Text))
{
if (message.Text.Equals("reset", StringComparison.InvariantCultureIgnoreCase))
{
return message.Text;
}
}

return null;
}

protected override bool HasScore(IActivity item, string state)
{
return state != null;
}

protected override double GetScore(IActivity item, string state)
{
return 1.0;
}

protected override async Task PostAsync(IActivity item, string state, CancellationToken token)
{
this.task.Reset();
botData.UserData.Clear();
botData.PrivateConversationData.Clear();
await botData.FlushAsync(token);
}
protected override Task DoneAsync(IActivity item, string state, CancellationToken token)
{
return Task.CompletedTask;
}
}
Then I create GlobalMessageHandlersBotModule
public class GlobalMessageHandlersBotModule : Module
{
protected override void Load(ContainerBuilder builder)
{
base.Load(builder);

builder
.Register(c => new CancelScorable(c.Resolve(), c.Resolve()))
.Asdouble>>()
.InstancePerLifetimeScope();
}
}
At last I registried in GlobalAsax
protected void Application_Start()
{
    this.RegisterBotModules();

    GlobalConfiguration.Configure(WebApiConfig.Register);
}

private void RegisterBotModules()
{
    var builder = new ContainerBuilder();

    builder.RegisterModule(new ReflectionSurrogateModule());

    builder.RegisterModule();

    builder.Update(Conversation.Container);
}
I hope this can help you!
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