LINQ to SQL

LINQ to SQL allows .NET developers to write “queries” in their .NET language of choice to retrieve and manipulate data from a SQL Server database. In a general sense, LINQ to SQL allows us to create SQL queries in our preferred .NET language syntax and work with a strongly types collection of objects as a return result. We can make changes to these objects then save changes back to the database.


Example Query

HookedOnLINQ db =
new HookedOnLINQ("Data Source=(local);Initial Catalog=HookedOnLINQ");

var q = from c in db.Contact
where c.DateOfBirth.AddYears(35) > DateTime.Now
orderby c.DateOfBirth descending
select c;

foreach(var c in q)
Console.WriteLine("{0} {1} b.{2}",
c.FirstName.Trim(),
c.LastName.Trim(),c.DateOfBirth.ToString("dd-MMM-yyyy"));

Output:
Mack Kamph b.17-Sep-1977
Armando Valdes b.09-Dec-1973

The moment we entered the foreach loop (that’s important, the SQL was only executed the first time we requested data, until then the query was just kept in-memory as an expression, this is called Deferred Execution), the following SQL Statement was formulated by LINQ and executed on the server.

SELECT [t0].[ContactId], [t0].[FirstName], [t0].[LastName], [t0].[DateOfBirth],[t0].[Phone], [t0].[Email], [t0].[State]
FROM [Contact] AS [t0]
WHERE DATEADD(YEAR, @p0, [t0].[DateOfBirth]) > @p1
ORDER BY [t0].[DateOfBirth] DESC