LINQ

...

LINQ

Microsoft SQL Server 2008 LINQ enables developers to build queries over data directly from within any .NET-based programming language.

LINQ to Entities, LINQ to DataSet, LINQ to SQL, and LINQ to XML are key implementations of this powerful technology.

Use:

LINQ to SQL for objects mapped directly to Microsoft SQL Server database schemas
LINQ to XML for XML data
LINQ to Entities for entity objects mapped to ADO.NET Data ProvidersLINQ to DataSet to work with existing DataSet functionality

Community Links

MSDN Forum: LINQ

MSDN Forum: LINQ to Entities

MSDN Forum: LINQ to SQL

MSDN Forum: LINQ to Xml

MSDN: 101 LINQ Samples

Great Microsoft resource, demonstrating many LINQ constructs.

Unfortunately, not really focused on the delegate way of doing things :-( -- and also just focused on LINQ, and not enough LINQ to SQL.

But it's still a great resource...

MSDN: Linq

The MSDN Entry Point...

About LINQ to SQL

The concepts behind LINQ to SQL are great (and I'm not just referring to the fact that it was free, and built into the Framework).

Unfortunately, the execution and rollout was...mediocre.

The end result is that after milliions of advertising, fanfare, etc., Microsoft is killing it, or at least rolling it into other Microsoft technologies. They're not saying that you have to immediately stop coding with it, or worse, update any code that you have written that relies on it (it will be around for a while), but that if you are starting a new project, that you should look around for an alternate solution...

One of the problems that it faced were that it was considered good, but not great in terms of execution.
For heavy traffic websites it was maybe a bit light
Another issue -- and fundamental, in my case -- was that it wasn't as global as the name implied. It really was only for SQL...as in SQL Server. Nor was it ported to the Compact Framework...

All to say that I love the technology...it glitters...it promises much...but I'm still holding my breath waiting for a time when I have in the framework an reliable, performant ORM that abstracts the DL completly, for any DBMS, on both the full and compact framework...

As you can imagine...I'm slowly turning blue...

Links to Tools

Linq to SQL (Portable)

A CodeProject article worth following up on (even if LINQ to SQL is being phased into other things by Microsoft): the is attempting to make a SQL-92 (ie portable) LINQ to SQL that works with othe DBs than just SQL Server ("SQLite, SQLServer 2000/2005, Microsoft Access, MySQL"). I havn't tested it, but worth knowing about.

Although still doesn't solve my problem of needing LINQ to SQL on Compact Framework...grumble!

LinqPad

An absolute essential tool to learning Linq, and Linq to SQL.

Visual LINQ Query Builder

An add-in to Visual Studio 2008 Designer that helps you visually build LINQ to SQL queries.
Similar to MS Access Query Builder, but in the LINQ domain.
Output is rendered in WPF.

Good stuff

Using LINQ to SQL with Unity (DI)

More advanced concepts worth considering, once you've got LINQ to SQL down...

Using-LINQ-for-querying-collections

Where can I learn LINQ?

FAQs about working with ORMs in general

Questions about how Repositories should be designed to work with ORMs

The Repository Pattern works with Query Objects to abstract access to the Data Mapper Layer.
This post demonstrates basics to stop it from leaking all over the BL.

LINQ to SQL FAQs

Linq To SQL relies on Lazy Loading unless I specify otherwise...how do I prefetch attached tables?

Should I use vars for custom query results, and if so how do I return anon types beyond the method they were created in?

Are the generated Entities the Business Objects?

How can I log the output of what LINQ to SQL is doing?

How do I handle mapping Enums to an database, without LINQ to SQL converting it to an Int datatype?

What are Dynamic queries, and how do I use them?

LINQ to SQL Links

CodeProject: Intro to (practical) LINQ

A surprisingly good intro to LINQ to SQL, that should be read after/before/with the 5 minute overview article...It gives practical tips for Types, etc.

Fundamental Questions answered

Read this. Slowly. Chock full of answers for people freaking out about how ORM fits in the picture, how to write the DAL layer, whether to isolate it, how, etc.

Really excellent.

LINQ to SQL - 5 Minute Overview

Excellent summary of basic points.

LinqPad

Absolutely essential for getting up to speed on LINQ in general, but also LINQ to SQL.

Why LINQ beats SQL

An absolutly clear *must* read for anybody having hesitations and final questions about why LINQ is simply far better than working with SQL.

LINQ to Entities

LINQ to Entities vs. LINQ to SQL - What should I use and when?

Interesting post suggesting why weaning yourself off of Linq to SQL and moving on up to Linq to Entities could be a good thing (and this was written back in 2006!).