Send Hero or Adaptive card & Get User Input on Welcome - botframework

Question

I am developing Bot in .NET Core 3.1 C#. I want to send Hero card with 4 buttons & welcome prompt as soon as user joins /activates bot. I have tried it in OnMembersAddedAsync
if (member.Id != turnContext.Activity.Recipient.Id)
{
var welcomeCard = CreateAdaptiveCardAttachment();
var response = MessageFactory.Attachment(welcomeCard);
await turnContext.SendActivityAsync( response, cancellationToken);
}
This will display adaptive card where type is Action.Submit. But I am not sure how to get values of the button which customer click on. I tried it on OnMessageActivityAsync
if (turnContext.Activity.Value != null)
{
var mainMenu = turnContext.Activity.Value;
}
But values are always null. Json for adaptive card is :
{
"$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
"type": "AdaptiveCard",
"version": "1.0",
"body": [
{
"type": "TextBlock",
"spacing": "medium",
"size": "default",
"weight": "bolder",
"text": "Welcome to ABC Bank !",
"wrap": true,
"maxLines": 0
},
{
"type": "TextBlock",
"size": "default",
"isSubtle": true,
"text": "Please select user type from below ....",
"wrap": true,
"maxLines": 0
}
],
"actions": [
{
"type": "Action.Submit",
"title": "Consumer"
},
{
"type": "Action.Submit",
"title": "Client"
},
{
"type": "Action.Submit",
"title": "Merchant"
}
]
}

Answer 1

Yes. As said in comments you need to add data property. This is not required. But if you want to collect which option user has provided you need to specify it. Since you don't have any other input field. This will act as an input to carry further operations.
Note: For any input element you need to use id property to identify collected input when submit action is performed.
Similarly for Submit action data. Make sure value in data for each action is unique. If you want 2 buttons to perform same action (nativate to same dialog) then you can specify same value in data
Here is the official link which gives you an idea.
Submit action
Hope this helps