Unable to send Attachment in Webchat using directline, same code is working fine in emulator

Question

var response = MessageFactory.Attachment(new Attachment
{
     Name = @"application.png",
     ContentType = "image/png",
     ContentUrl =  "base64sting"
});

await dc.Context.SendActivityAsync(response);

Above code throwing the below exception in webchat when i try to send attachment to user , in emulator it is working fine

at Microsoft.Bot.Connector.Conversations.ReplyToActivityWithHttpMessagesAsync(String conversationId, String activityId, Activity activity, Dictionary`2 customHeaders, CancellationToken cancellationToken) in D:\a\1\s\libraries\Microsoft.Bot.Connector\Conversations.cs:line 1121

at Microsoft.Bot.Connector.ConversationsExtensions.ReplyToActivityAsync(IConversations operations, String conversationId, String activityId, Activity activity, CancellationToken cancellationToken) in D:\a\1\s\libraries\Microsoft.Bot.Connector\ConversationsExtensions.cs:line 241

at Microsoft.Bot.Builder.BotFrameworkAdapter.SendActivitiesAsync(ITurnContext turnContext, Activity[] activities, CancellationToken cancellationToken) in D:\a\1\s\libraries\Microsoft.Bot.Builder\BotFrameworkAdapter.cs:line 316

at Microsoft.Bot.Builder.TurnContext.<>c__DisplayClass22_0.d.MoveNext() in D:\a\1\s\libraries\Microsoft.Bot.Builder\TurnContext.cs:line 267

I even tried this

using (var connector = new ConnectorClient(new Uri(serviceUrl)))
{
    var attachments = new Attachments(connector);
    var response = await attachments.Client.Conversations.UploadAttachmentAsync(
        conversationId,
        new AttachmentData
        {
            Name = @"Resources\architecture-resize.png",
            OriginalBase64 = File.ReadAllBytes(imagePath),
            Type = "image/png",
        }
    );

    var attachmentUri = attachments.GetAttachmentUri(response.Id);

    return new Attachment
    {
        Name = @"Resources\architecture-resize.png",
        ContentType = "image/png",
        ContentUrl = attachmentUri,
    };
}

this is failing as well, is there any work around to send attachment to user using webchat without having hosted content url?

Answer 1

For those who are facing this issue , below is the root cause.

I was trying to send image as an item to click and save, i think i figured out the issue, directline supports only 4MB message size, the base64string of my image is very large , causing the message to exceed 4MB, now am uploading the image to azure blob and using the blob uri as contentURI , it is working now