When Will Use IDataReader And DataReader ?

Let me try to answer your question: 

 

Your doubt can be cleared if you understand inheritance concept of object oriented programming.

 

IDataReader is just an interface, so technically you cannot use it.

Both DbDataReader and SqlDataReader implement the interface IDataReader.

 

You will use the DbDataReader implementation, if you are using any relational data source other than SQL Server

 

You will use the SqlDataReader implementation, if you are using SQL Server as your relational data source.

 

If you are writing a product which will have to connect to either Oracle or SQL Server as per users choice, you will use IDataReader as a base type to use both DbDataReader and SqlDataReader.

 

I hope you understand! If not, please tell which part.