How do you handle concurrency and data consistency in a multi-user environment?

In a multi-user environment, concurrency and data consistency are crucial. In .NET, we can handle concurrency by using techniques like optimistic concurrency control or pessimistic concurrency control. Optimistic concurrency involves detecting conflicts at the time of data modification, while pessimistic concurrency involves locking data during modification to prevent conflicts. Additionally, we can ensure data consistency by using transactions, ACID properties, and appropriate isolation levels in database transactions.