Comfortable persistence for .NET
NDO® (.NET Data Objects) is a very elegant object-relational mapping (OR) development tool on the .NET platform. With the help of NDO, normal .NET classes become persistent classes whose instances are stored in any relational databases.
All means of object-oriented programming (OOP) are available to you, such as inheritance and polymorphism. However, your data is stored in relational databases with a meaningful structure, which you can access with any application.
NDO is Open Source und free. You can find it here on Github.