LINQ to SharePoint in SharePoint 2010 using SPMETAL

Introduction

In SharePoint 2010 you now have the ability to use LINQ syntax to fetch items from your lists instead of using the "traditional" approach of CAML queries. (Including SPSiteDataQuery and SPQuery objects)

In this article I will give you a brief introduction to how you can get started using LINQ queries in SharePoint, also known as LINQ to SharePoint.

Basics of LINQ?

As a prerequisite to this article, I'm going to imply that you know what LINQ is and how to write basic LINQ queries in any .NET application already. I'm not going to dive into the details about LINQ or the syntax itself here - please see MSDN for that!

LINQ to SharePoint!

In order to work with LINQ in SharePoint 2010, we need use a tool called SPMetal.exe which resides in the 14\bin folder. This tool is used to generate some entity classes which Visual Studio 2010 can use to get IntelliSense, and allows for LINQ-based queries to be performed on your lists.

Noteworthy:

• LINQ to SharePoint queries are translated to proper CAML queries
• CAML queries are in turn later translated to SQL queries

SPMetal.exe

Using the tool called SPMetal, we generate our entity-classes that are needed to perform these object oriented queries toward our SharePoint server.

These are the required steps to get hooked up:

1. Launch a cmd-window and navigate to C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\bin
   
   
2. Run the following command to utilize the SPMetal.exe tool with the following syntax:
1. SPMetal.exe /web:http://yoursite /code:C:\YourEntityFile.cs
2. Example:
   
   
3. Now navigate to C:\ (or wherever you chose to output your file) and make sure the file has been generated:
   
   
4. Open up the file and take a look at the content that SPMetal now have provided us with:
   
   Note that the class name is now MyEntitiesDataContext. It's based on the name you specify as your code file in the SPMetal.exe command line tool.
   
   If you were to use /code:C:\Awesome.cs instead, it would generate a class calledAwesomeDataContext.

With that done - all we need to do is import it to one of our projects and use it!

Visual Studio 2010 - Let's create a sample Web Part that utilizes LINQ to SharePoint

In this sample I will create a simple Web Part that will use LINQ to SharePoint syntax to fetch some information from the Announcements list. A basic sample I use in my training classes as well, and should be fairly easy to grasp!

1. Create a new project (I'm going to create a new Visual Web Part project)
2. Import your DataContext-file by choosing your Project -> Add -> Existing Item:
3. Specify your file (mine is called MyEntities.cs):
4. Make sure it's properly placed in your project structure - then we're good to go:
   

Alright - that's easy enough. Thus far we have created an entity file using SPMetal.exe and now we have successfully imported it into our project.

Add proper references

Now in order to use LINQ to SharePoint, you also need to reference the Microsoft.SharePoint.Linqassembly. Point to references, right-click and choose "Add Reference" and select the Microsoft.SharePoint.Linq.dll file:

In your code, reference the assemblies:

Ready to code?

What you should've done up until now is this:

1. Generate your entities using the SPMetal.exe tool
2. Reference the newly created file from your SharePoint project
3. Make sure you're using the proper references for System.Linq and Microsoft.SharePoint.Linq
4. Be ready to code :-)