http://www.linq-to-sql.com Linq guide for DEVELOPERS Sun, 29 Jun 2008 11:11:19 +0000 http://backend.userland.com/rss092 en LINQ is a programming model that introduces queries as a first-class concept into any Microsoft .NET language. However, complete support for LINQ requires some extensions in the language used. These extensions boost productivity, thereby providing a shorter, meaningful, and expressive syntax to manipulate data. Following is a simple LINQ query for a ... http://www.linq-to-sql.com/linq-to-sql/what-is-linq/ If you want to add a record to a table or remove a record from a table, creating or deleting an object in memory is not enough. The DataContext instance must be notified also. This can be done directly by calling Add or Remove on the corresponding Table collection (these ... http://www.linq-to-sql.com/linq-to-sql/linq-insert-sample/ One of the most frequently asked query type is outer join. With T-Sql by using 'left outer join' type it was possible to get the records of the Customer table without the orders. T-Sql usage: select c.ContactName, OrderID= case when o.OrderID is null then '(no orders)' else convert(varchar,o.OrderID) end from Customers c left outer ... http://www.linq-to-sql.com/linq-to-sql/t-sql-to-linq-upgrade/linq-outer-join/ If you newbie to linq, you should download and install some tools for trying samples and developing apps. Visual Studio 2008 and Sql Server express editions: http://www.linq-to-sql.com/linq-to-sql/t-sql-to-linq-upgrade/linq-download-vs2008-sql2005/ T-Sql coalesce usage: select c.ContactName, EmpID= coalesce(o.EmployeeID,-1) from Customers c left outer join Orders o on o.CustomerID = c.CustomerID Same Query with Linq ?? operator: http://www.linq-to-sql.com/linq-to-sql/t-sql-to-linq-upgrade/linq-null-coalesce/ T-Sql exists Usage: select c.CompanyName, o.* from Customers c join Orders o on o.CustomerId = c.CustomerId where o.ShipCountry = 'Germany' Linq contains usage instead of exists: DataClassesDataContext db = new DataClassesDataContext(); var Cust = from c in db.Customers join o in db.Orders on c.CustomerID equals o.CustomerID where o.ShipCountry == "Germany" select new { c.CompanyName, o.OrderDate, o.ShipCountry }; http://www.linq-to-sql.com/linq-to-sql/t-sql-to-linq-upgrade/linq-join/ T-Sql exists Usage: select * from Customers c where exists(select * from Orders where ShipCountry = 'Germany' and CustomerId = c.CustomerId) Linq contains usage instead of exists: DataClassesDataContext db = new DataClassesDataContext(); var Cust = from c in db.Customers where (from o in db.Orders where o.ShipCountry == "Germany" select o.CustomerID).Contains(c.CustomerID) select c; http://www.linq-to-sql.com/linq-to-sql/t-sql-to-linq-upgrade/linq-exists/