Clear explanation of Dialog implementation on bot framework V4

Question

Is there someone who can explain how to code dialog from bot framework properly? I'm trying to code from scratch using the empty bot template to understand every pieces of code and why and how they piece together. But even after reading so many times I don't how it is properly implemented or coding for dialogs in Microsoft Bot Framework. I've read the documentation from microsoft many times and many version or doc from microsoft but still can't comprehend how it link together every piece of code. Even blogs or website i found did not explain why such pieces of code is needed but just ask you to add this and that. I understand concept but not the mechanics. The code seems to span from startup.cs, yourMainBotLogic.cs, dialogClassName.cs, BotAccessors.cs which confuse me which are the steps the program is run on and how.

Please explain in detail why the pieces of code/components is needed/what use it has and why it has to be there in such files (e.g. Startup.cs). For example;

var accessors = new BotAccessors(conversationState) { ConversationDialogState = conversationState.CreateProperty<DialogState>("DialogState"), }; return accessors;

Create a accessor for the DialogState and then return it. This is just example and my description of the code might not be right.

Eric Dahlvang Eric Dahlvang · Accepted Answer · 2019-02-01T20:37:40

Your question about how everything fits together is a bit broad, but I will attempt some explanation:

startup.cs: bot configuration should be loaded here, and singletons created. Including IStatePropertyAccessors. Many of the samples contain a BotConfig file with bot specific setup code, and call it from startup. Many samples also contain a bot file. Bot files can make loading some bot services easier. But, they aren't necessary. Ids and passwords can still be retrieved from App Settings, or web.config and your code can create the services.

Some things usually initialized in startup are:

ICredentialProvider is used by the sdk to create the BotAdapter and provide JWT Token Auth. For single appid/password bots, the SDK provides a SimpleCredentialProvider. If your bot is using the integration libraries, you can create one during the IBot initialization, or just supply the botConfig with appid/pass:

webapi:

    public static void Register(HttpConfiguration config)
    {
         config.MapBotFramework(botConfig =>
        {
          var appId = ConfigurationManager.AppSettings[MicrosoftAppCredentials.MicrosoftAppIdKey];
          var pass = ConfigurationManager.AppSettings[MicrosoftAppCredentials.MicrosoftAppPasswordKey];

          botConfig.UseMicrosoftApplicationIdentity(appId, pass);
        }
    }

netcore:


    public void ConfigureServices(IServiceCollection services)
    {
       services.AddBot(options =>
     {
        options.CredentialProvider = new SimpleCredentialProvider(appId, appPassword);
     });           
    }

IStorage is an implementation for interacting with a state store. The sdk provides MemoryStorage CosmosDbStorage and AzureBlobStorage These are each just using JsonSerializer to store and retrieve objects from the underlying storage.

BotState are objects that provide keys into the IStorage implementation. The SDK provides three examples:
- ConversationState scoped by {channelId}/conversations/{conversationId}
- UserState scoped by {channelId}/users/{userId}
- PrivateConversationState scoped by {channelId}/conversations/{conversationId}/users/{userId}

IStatePropertyAccessors These are an implementation layer providing for typed access into the scoped BotState explained above. When a get/set is performed, the actual state store is queried and persisted (through an internal cache provided by the sdk).

BotAccessors.cs is just a container to hold the state classes and IStatePropertyAccessors. This isn't needed, but is for convenience.

yourMainBotLogic.cs: this is where the adapter's OnTurn implementation exists, and should load the dialog stack and process the user's message. The dialog stack is managed by a dialog set that contains an IStatePropertyAccessor of DialogData type. When a get is performed on this property accessor by calling create context, the state store is queried to fill the dialog stack of the DialogContext.

dialogClassName.cs is a dialog implementation. The specific dialog types are delineated here: Dialog types Examples of how to use them are in the samples on github and documentation.

As with other asp.net applications, startup is run when the application first loads (see aspnet-web-api-poster or lifecycle-of-an-aspnet-mvc-5-application and note that the Microsoft.Bot.Builder.Integration.AspNet.Core uses an IApplicationBuilder extension to add the message handler to the request pipeline ApplicationBuilderExtensions and Microsoft.Bot.Builder.Integration.AspNet.WebApi uses an HttpMessageHandler implementation). However, you can choose to not use the integration libraries, and create your own controllers. Like this sample: MVC-Bot

V4 additional references

Clear explanation of Dialog implementation on bot framework V4

1 Answers