You can send contact information via MMS using C# and .NET by setting up a Twilio account, creating a file hosting service, and using the Twilio SDK to send an MMS message with a vCard attachment. To start, you need to obtain your Twilio credentials, buy a phone number, set up a messaging service, create a static file host, and configure your .NET project. You then generate contact information in vCard format using the vCardLib library, save it as a file, and share it over MMS using the Twilio SDK. The message can be scheduled to send at a later time, allowing you to control when the message is sent. To further improve this functionality, you could add more information about the contact in the vCard, use a real static file host service, or add webhooks to check the final status of the message.