instructions.md

You are back working on the ORM (Object Relationship Mapping) system introduced in (TODO cross-reference-tba).

Our ORM usage analysis shows that 95% of transactions are executed from within one calling method, and it has been decided that it would be more appropriate to have a single ORM method that opened, wrote and committed a transaction.

The database has the following instance methods:

• Database.BeginTransaction() starts a transaction on the database.
• Database.Write(string data) writes data to the database within the transaction. If it receives bad data an exception will be thrown. An attempt to call this method without BeginTransction() having been called will cause an exception to be thrown. If successful the internal state of the database will change to DataWritten.
• Database.Commit() commits the transaction to the database. It may throw an exception if it can't close the transaction or if Database.BeginTransaction() had not been called.
• A call toDatabse.Dispose() will clean up the database if an exception is thrown during a transaction. This will change the state of the database to Closed.

1. Write to the database

Implement the Orm.Write() method to begin a database transaction, write the data passed in and commit the transaction. All exceptions including InvalidOperationException should be allowed to pass to the caller without logging or any other intervention.

Database db = new Database();
Orm orm = new Orm(db);
orm.Write("good write");
// => database has an internal state of State.Closed
orm.Write("bad write");
// => an exception is thrown but database is left with an internal state of State.Closed
orm.Write("bad commit");
// => an exception is thrown but database is left with an internal state of State.Closed

2. Write to the database and return an indication of whether the write was successful to the caller

It has been a few months since Orm.Write() was introduced and there is division in the team. Many developers would like the ORM to handle errors when exceptions are thrown and simply return an indication of success to the caller.

Please implement the Orm.WriteSafely() method to begin a database transaction, write the data passed in and commit the transaction (as above). It should return true if the write was successful, otherwise false. Do not attempt to log the exception.

Database db = new Database();
Orm orm = new Orm(db);
orm.WriteSafely("good write");
// => true
orm.WriteSafely("bad write");
// => false
orm.WriteSafely("bad commit");
// => false