To access a database, we need to open a connection to it first and close it once our job is done. Connecting to a database depends on the type of the target database and the database management system (DBMS). For example, connecting to a SQL Server database is different from connecting to an Oracle database. But both these connections have a few things in common: • They have a connection string • They can be opened • They can be closed • They may have a timeout attribute (so if the connection could not be opened within the timeout, an exception will be thrown). Your job is to represent these commonalities in a base class called DbConnection. This class should have two properties: ConnectionString : string Timeout : TimeSpan A DbConnection will not be in a valid state if it doesn’t have a connection string. So you need to pass a connection string in the constructor of this class. Also, take into account the scenarios where null or an empty string is sent as the connection string. Make sure to throw an exception to guarantee that your class will always be in a valid state. Our DbConnection should also have two methods for opening and closing a connection. We don’t know how to open or close a connection in a DbConnection and this should be left to the classes that derive from DbConnection. These classes (eg SqlConnection or OracleConnection) will provide the actual implementation. So you need to declare these methods as abstract. Derive two classes SqlConnection and OracleConnection from DbConnection and provide a simple implementation of opening and closing connections using Console.WriteLine(). In the real-world, SQL Server provides an API for opening or closing a connection to a database. But for this exercise, we don’t need to worry about it.