Beginning ASP.NET 3.5: In C# and VB

13.6. Summary

LINQ is a compelling and exciting new technology that ships with .NET 3.5. LINQ is going to take a big place in many data-access scenarios, including database access in ASP.NET web applications using LINQ to SQL.

Because LINQ is going to be so important, it has been integrated in many different places in .NET. LINQ is available for objects allowing you to query in-memory collections. Additionally, LINQ is available for XML, Entities, and DataSets, each type providing access to a different data store, but with the same, unified querying language. The final type of LINQ is LINQ to SQL that provides access to your SQL Server database.

To write LINQ queries, you use query operators that include keywords like Select, From, and Where and aggregation operators like Sum and Count. To get data out of a LINQ query you can use type inference to let the compiler determine the resulting type. This also allows you to create anonymous types, where the actual type returned by the query doesn't have a name, but its public interface is inferred by the compiler, giving you IntelliSense at compile time, and full access to the object at run time.

To work with LINQ to SQL in your ASP.NET web applications you have a couple of different options. First, you can write queries in the Code Behind of a page and then bind the results to a data-bound control using the DataSource property and DataBind method of the control. Although this method gives you a lot of flexibility in terms of the queries ...