SharePoint 2010 – LINQ and SPMetal

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Introduction

In this article we explore some advanced programming areas:

• LINQ to SharePoint
• SPMetal

LINQ to SharePoint is a new feature of SharePoint 2010. LINQ stands for Language Integrated Query which is a part of .NET. The aim of LINQ is to support different data sources using the same Typed Query Syntax. Presently it supports Objects, Datasets, SQL, Entities, XML, etc.

Why do we need LINQ?

You might have noted that the previous List Programming examples did not use proper column name access. LINQ allows us to access the List in a Typed manner.  Adding more clarity we can access the list items based on the column names which we usually do with databases.

Example:

var result = from c in Citizen where c.Name == "John" select c;

What is SPMetal?

As we will be creating custom lists having custom column names, we need to generate the Entity Model. SPMetal.exe is the tool which helps in generating Model classes. Although we can create Model classes manually, it will be a tedious job and error prone. Using SPMetal would be the right approach to model classes.

Activities

Following are the activities performed in this article:

1. Manager List Creation
2. Entity Creation
3. Read using LINQ
4. Insert Entity
5. Update Entity
6. Delete Entity

Experimenting with LINQ and SPMetal

To start with, create a custom list inheriting from Custom List and name it Manager. Add the following custom columns and data:

Generating the Entity Models

Now we can generate the Entity Model for the above List. You can get SPMetal.exe inside the following folder: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\BIN.

Open a command prompt and go to the specified folder:

Now run the following command:

SPMetal.exe /web:http://YOURSITE /code:SiteEntities.cs 

Wait for a while and you will be ready with the new file. Open the file SiteEntities and you can see the Manager class is contained inside.

Create Application

Create a new SharePoint > 2010 > Console Application (targeting the .NET 3.5 framework) and add the SiteEntities.cs file into it.

Add a reference to the following assembly:

You can try the following operations: Read, Insert, Update, Delete using LINQ to SharePoint.

Selecting an Item

Now we are trying to select the managers with country as USA:

using (SiteEntitiesDataContext context = new SiteEntitiesDataContext("http://appes-pc"))
{
    var result = context.Manager.Where(m => m.Country == "USA");

    foreach (ManagerItem manager in result)
    {
        Console.WriteLine(manager.Name);
    }
}

Note: You can use LINQ or Lambda Expression to do the query. In the above example I have used Lambda.

On executing the application you can see the following results.

Inserting an Item

For inserting a new item into the Manager list, use the following code:

using (SiteEntitiesDataContext context = new SiteEntitiesDataContext("http://appes-pc"))
{
    ManagerItem manager = new ManagerItem();
    manager.Name = "New Manager";
    manager.Address = "New Address";
    manager.Country = "New Country";

    context.Manager.InsertOnSubmit(manager);
    context.SubmitChanges();
}

After executing the application, open the Manager list inside SharePoint as shown below:

Updating an Item

For updating an item inside SharePoint, use the following code:

using (SiteEntitiesDataContext context = new SiteEntitiesDataContext("http://appes-pc"))
{
    ManagerItem manager = context.Manager.Where(m =>  
                          string.IsNullOrEmpty(m.Title)).FirstOrDefault();
    if (manager != null)
        manager.Title = "New Title";

    context.SubmitChanges();
}

You can see the updated entity inside SharePoint:

Deleting an Item

For deleting an item inside SharePoint use the following code:

using (SiteEntitiesDataContext context = new SiteEntitiesDataContext("http://appes-pc"))
{
    ManagerItem manager = context.Manager.Where(m => m.Title.Length > 3).FirstOrDefault();
    if (manager != null)
        context.Manager.DeleteOnSubmit(manager);

    context.SubmitChanges();
}

You can see that the item is deleted inside SharePoint:

This concludes our Read, Insert, Update, Delete operations using LINQ to SharePoint. Hope the topics are understood by the reader.

Summary

In this article we have explored LINQ and the SPMetal tool. This information is necessary in real world programming scenarios. The attachment contains the source code we discussed.

References

• http://msdn.microsoft.com/en-us/library/ee535491.aspx
• http://msdn.microsoft.com/en-us/library/ee538255.aspx