Entity Framework

Entity Framework is an Object Relational Mapper (ORM). It basically generates business objects and entities according to the database tables and provides the mechanism for:

1. Performing basic CRUD (Create, Read, Update, Delete) operations.
2. Easily managing "1 to 1", "1 to many", and "many to many" relationships.
3. Ability to have inheritance relationships between entities.

and to answer the second question, the benefits are:

1. We can have all data access logic written in higher level languages.
2. The conceptual model can be represented in a better way by using relationships among entities.
3. The underlying data store can be replaced without much overhead since all data access logic is present at a higher level.

and finally, the last question that whether it is an alternative to ADO.NET, the answer would be "yes and no". Yes because the developer will not be writing ADO.NET methods and classes for performing data operations and no because this model is actually written on top of ADO.NET, meaning under this framework, we are still using ADO.NET. So let us look at the architecture of Entity Framework (diagram taken from MSDN):

LINQ to SQL allow you to query and modify SQL Server database by using LINQ syntax. Entity framework is a great ORM shipped by Microsoft which allow you to query and modify RDBMS like SQL Server, Oracle, DB2 and MySQL etc. by using LINQ syntax. Today, EF is widely used by each and every .NET application to query to database. The difference between LINQ to SQL and EF is given below.

LINQ to SQL

Entity Framework

It only works with SQL Server Database.

It can works with various databases like Oracle, DB2, MYSQL, SQL Server etc.

It generates a .dbml to maintain the relation

It generates an .edmx files initially. The relation is maintained using 3 different files .csdl, .msl and .ssdl

It has not support for complex type.

It has support for complex type.

It cannot generate database from model.

It can generate database from model.

It allows only one to one mapping between the entity classes and the relational tables /views.

It allows one-to-one, one-to-many & many-to-many mappings between the Entity classes and the relational tables /views

It allows you to query data using DataContext.

It allows you to query data using EntitySQL, ObjectContext, DbContext.

It provides a tightly coupled approach.

It provides a loosely coupled approach. Since its code first approach allow you to use Dependency Injection pattern which make it loosely coupled .

It can be used for rapid application development only with SQL Server.

It can be used for rapid application development with RDBMS like SQL Server, Oracle, DB2 and MySQL etc.