How to receive an image send by users?

I am programming a chatbot and I want the user to upload an image so that the bot can receive it and save the image into the User profil data. But I am quite new in c# and I am a bit lost...

I am using the MS Bot Framework. To build the dialog, I use Waterfall Step and to catch the user reply, I use Prompt. To receive attachment I saw on MS documents that it exists an AttachmentPrompt class. But I am a bit confused on how to use it and how I can save the file in the user profil.

This is how I build the waterfall dialog :

public class MainDialog : ComponentDialog
{
    // Prompts names
    private const string PhotoPrompt = "PhotoPrompt";

    // Dialog IDs
    private const string ProfileDialog = "profileDialog";


    public MainDialog(IStatePropertyAccessor<IncidentFile> IncidentFileStateAccessor, ILoggerFactory loggerFactory)
        : base(nameof(MainDialog))
    {
        IncidentFileAccessor = IncidentFileStateAccessor ?? throw new ArgumentNullException(nameof(IncidentFileStateAccessor));

        // Add control flow dialogs
        var waterfallSteps = new WaterfallStep[]
        {
                InitializeStateStepAsync,
                PromptForPhotoStepAsync,
                DisplayGreetingStateStepAsync,
        };
        AddDialog(new WaterfallDialog(ProfileDialog, waterfallSteps));
        AddDialog(new AttachmentPrompt(PhotoPrompt));

    }

Then, here is the function that catch the Prompt:

private async Task<DialogTurnResult> PromptForPhotoStepAsync(WaterfallStepContext stepContext,CancellationToken cancellationToken)
    {
        var IncidentState = await IncidentFileAccessor.GetAsync(stepContext.Context);
        if (string.IsNullOrWhiteSpace(IncidentState.Photo))
        {
            // prompt for Photo, if missing in User profil
            var opts = new PromptOptions
            {
                Prompt = new Activity
                {
                    Type = ActivityTypes.Message,
                    Text = "Can you send me a photo please?",
                },
            };
            return await stepContext.PromptAsync(PhotoPrompt, opts);
        }
        else
        {
            return await stepContext.NextAsync();
        }

    }

And this is how I save the user data :

public class IncidentFile
{
    public string Name { get; set; }
    public string Photo { get; set; }

}

I don't know if I use correctly the AttachmentPrompt class. I also don't know how the Attachment prompt is sending the image to the bot, so in the IncidentFile, I put "public string" for the Photo, but I don't know if it should be a byte array, or the path of the image location or else. But anyway, after I test it and i upload a photo, the bot reply that something went wrong...

Thank you for your time!

You're so close! Once the user uploads the photo, you can access it in the next Waterfall step with stepContext.Result:

As you can see, the type is Microsoft.Bot.Schema.Attachment, so change your IncidentFile to:

using Microsoft.Bot.Schema;

namespace <your-namespace>
{
    public class IncidentFile
    {
        public string Name { get; set; }
        public Attachment Photo { get; set; }
    }
}

You save that information in the step following the upload step with something like:

// Load the IncidentFile
var incidentFile = await IncidentFileAccessor.GetAsync(stepContext.Context);
// Save the photo
incidentFile.Photo = ((List<Attachment>)stepContext.Result)[0];
await IncidentFileAccessor.SetAsync(stepContext.Context, incidentFile);

Result:

References

C# Samples. I'd link to specific ones, but we're about to delete some and reorganize this repo. However, look at:
- Basic Bot (soon to be Core Bot) - Good for figuring out how to use user profiles
- Handling Attachments - General Attachment handling
Attachment Class
AttachmentPrompt Class