I'm using Microsoft Graph in C# to interact with the Azure AD, now I need to build a teams bot that sends a welcome message to the user that was added to the directory, even if the user hasn't had a previous conversation with the bot. How can I implement that if the conversation reference is null?
You would require to install the bot app using Graph API and then get the conversation reference to send welcome message.
See following reference: https://learn.microsoft.com/en-us/microsoftteams/platform/graph-api/proactive-bots-and-messages/graph-proactive-bots-and-messages?tabs=dotnet