The ADO.NET Entity Framework Overview

Every business application has, explicitly or implicitly, a conceptual data model that describes the various elements of the problem domain, as well as each element's structure, the relationships between each element, their constraints, and so on.

Since currently most applications are written on top of relational databases, sooner or later they'll have to deal with the data represented in a relational form. Even if there was a higher-level conceptual model used during the design, that model is typically not directly "executable", so it needs to be translated into a relational form and applied to a logical database schema and to the application code.

While the relational model has been extremely effective in the last few decades, it's a model that targets a level of abstraction that is often not appropriate for modeling most business applications created using modern development environments.

Let's use an example to illustrate this point. Here is a fragment of a variation of the AdventureWorks sample database that's included in Microsoft SQL Server 2005:


Figure 1
If we were building a human-resources application on top of this database and at some point wanted to find all of the full-time employees that were hired during 2006 and list their names and titles, we'd have to write the following SQL query:
SELECT c.FirstName, e.Title
FROM Employee e
INNER JOIN Contact c ON e.EmployeeID = c.ContactID
WHERE e.SalariedFlag = 1 AND e.HireDate >= '2006-01-01'

Let's say that another application, this time the sales system, is also built on top of the same database. Using the same logical schema we used in the previous example, we would have to use the following query to obtain all of the sales persons that have sales orders for more than $200,000:
SELECT SalesPersonID, FirstName, LastName, HireDate
FROM SalesPerson sp
INNER JOIN Employee e ON sp.SalesPersonID = e.EmployeeID
INNER JOIN Contact c ON e.EmployeeID = c.ContactID
INNER JOIN SalesOrder o ON sp.SalesPersonID = o.SalesPersonID
WHERE e.SalariedFlag = 1 AND o.TotalDue > 200000...






 

ADO.NET and Visual Studio

Functionality exists in the Visual Studio IDE to create specialized subclasses of the DataSet classes for a particular database schema, allowing convenient access to each field through strongly-typed properties. This helps catch more programming errors at compile-time and makes the IDE's Intellisense feature more beneficial.

 

ADO.NET.....

ADO.NET is a set of computer software components that programmers can use to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems, though it can also access data in non-relational sources. ADO.NET is sometimes considered an evolution of ActiveX Data Objects (ADO) technology, but was changed so extensively that it can be considered an entirely new product.