What is a deadlock in the context of databases?

Deadlock in databases is a situation where two or more transactions block each other, waiting for resources held by the other. As a result, none of the transactions can proceed, and the system 'hangs' in anticipation.

Example:

• Transaction A has acquired a lock on table X and is waiting for a lock on table Y.
• Transaction B has acquired a lock on table Y and is waiting for a lock on table X.

Both transactions cannot continue because each is waiting for the release of a resource held by the other.

To resolve deadlocks, DBMSs typically detect such situations and abort one of the transactions to unlock resources and allow other transactions to proceed.

In C#, when working with databases, it is important to manage transactions and locks properly, minimize the duration of lock holding, and use isolation levels to reduce the likelihood of deadlocks.