Types of transactions / levels of isolation?

In the context of C# and working with databases through ADO.NET or Entity Framework, transactions ensure the atomicity of operations.

Types of transactions:

• Local transactions — limited to a single database connection.
• Distributed transactions — span multiple resources (e.g., multiple databases), managed via MSDTC.

Transaction isolation levels:

• Read Uncommitted — allows reading uncommitted changes (dirty read).
• Read Committed — the default level, prevents reading uncommitted data.
• Repeatable Read — guarantees that data read during a transaction will not change until it completes.
• Serializable — the strictest level, prevents phantom reads, transactions are executed sequentially.
• Snapshot — uses versioning of data, avoids locking, reads a snapshot of data at the start of the transaction.

Example of setting the isolation level in C#:

using(var transaction = connection.BeginTransaction(IsolationLevel.Serializable))
{
    // database operations
    transaction.Commit();
}

Choosing the isolation level affects performance and data consistency, so it is important to select it based on the application's requirements.