SharePoint 2010 Client Object Model - C#, Silverlight, JavaScript Supported

You will see that the RowLimit is set to 3. On executing the query and displaying the results to a data grid you will see 3 items as shown below:

4. Get By Search Criteria

Now we can try selecting the list items using search criteria. Here we are trying to get the items of the Status as "In Progress".

ClientContext context = new ClientContext(ServerText.Text);
List list = context.Web.Lists.GetByTitle("Tasks");

CamlQuery query = new CamlQuery();
query.ViewXml = @"<View>
<Query>
<Where>
<Eq>
<FieldRef Name='Status'/>
<Value Type='Text'>In Progress</Value>
</Eq>
</Where>
</Query>
</View>";

ListItemCollection listItems = list.GetItems(query);
context.Load(listItems, items => items.Include(
item => item["Id"],
item => item["Title"],
item => item["Status"]
));
context.ExecuteQuery();

On executing the code above you will get the results filtered by the Status field.



5. Insert an Item

Here we can try inserting a new item into the Tasks list.

ClientContext context = new ClientContext(ServerText.Text);
Web web = context.Web;

List list = web.Lists.GetByTitle("Tasks");
ListItemCreationInformation newItem = new ListItemCreationInformation();
ListItem listItem = list.AddItem(newItem);
listItem["Title"] = "New Item Created through C#";
listItem.Update();

context.ExecuteQuery();

You can see that we are using a new class named ListItemCreationInformation along with the ListItem class. This information will be recorded and passed to the server once the ExecuteQuery() method is called.

On executing the above code and retrieving the results you will see the output as below:



6. Update an Item

The Update operation is next in the series of the CRUD pattern. Already we have seen updating the Title. Here you will see updating the Status.

ClientContext context = new ClientContext(ServerText.Text);
List list = context.Web.Lists.GetByTitle("Tasks");
CamlQuery query = new CamlQuery();
query.ViewXml = "<View/>";

ListItemCollection listItems = list.GetItems(query);

context.Load(listItems);

context.ExecuteQuery();

ListItem item = listItems[listItems.Count - 1];
item["Status"] = "In Progress";
item.Update();

context.ExecuteQuery();

On executing the code you will see that the last item was updated.

7. Delete an Item

Now we can try deleting an item from the List. Here is the code to achieve that.

ClientContext context = new ClientContext(ServerText.Text);
List list = context.Web.Lists.GetByTitle("Tasks");

ListItemCollection listItems = list.GetItems(new CamlQuery() { ViewXml = "<View/>" });
context.Load(listItems);
context.ExecuteQuery();

listItems[listItems.Count - 1].DeleteObject();
context.ExecuteQuery();

We need to call the DeleteObject() method of the item followed by the ExecuteQuery().

8. Reducing the Result Size by Specifying Properties

So what if you wanted only 1 property value for an item with 10 properties. There will be an unwanted transference of 9 columns. Here we can see how to specify only the necessary columns for an item.

ClientContext context = new ClientContext(ServerText.Text);
Web web = context.Web;

context.Load(web, w => w.Title);

context.ExecuteQuery();

MessageBox.Show("The title is: " + web.Title);
MessageBox.Show("Now trying to access a field not in Result Set (expect exception)");

try
{
MessageBox.Show(web.Description); // You will get Error here
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}

Here we can see that only the Title property has been specified for retrieval. Accessing the Description column throws an exception.

9. Reducing the Result Size in List

In the case of the list the problem is worse since there are n number of columns for the list. The result will be multiplied n times. So if we need only 1 column and retrieve 10 columns for a list of 1000 items, we end up getting 9 x 1000 unwanted column values.

So to specify the list columns in the Result Set the syntax will be slightly different.

ClientContext context = new ClientContext(ServerText.Text);
List list = context.Web.Lists.GetByTitle("Tasks");

CamlQuery query = new CamlQuery();
query.ViewXml = "<View/>";
ListItemCollection listItems = list.GetItems(query);

context.Load(listItems, items => items.Include(item => item["Id"]));

context.ExecuteQuery();

Please note the way Id is specified. While filling the results you should take care that only the Id column value is
accessed.

DataTable table = new DataTable();
table.Columns.Add("Id");

foreach (ListItem item in listItems)
table.Rows.Add(item.Id);

datagrid.DataSource = table;

10. Specifying Credentials

You can specify user Credentials while accessing the SharePoint server. The property Credentials is for this purpose.

ClientContext context = new ClientContext(ServerText.Text);
context.Credentials = new NetworkCredential("User", "Password");

Web web = context.Web;
context.Load(web);

context.ExecuteQuery();
MessageBox.Show(web.Title);

Please specify the correct user name and password of your site otherwise a Unauthorized Exception will be thrown.

So this concludes the article with Client Object Model examples for the most common scenarios. In the real world you will need much more complicated steps and I believe these will provide a base to achieve it.

When to use Server Object Model?

We can use it on the SharePoint server where the Server Object Model binaries are available. A typical example would be inside Web Parts / Workflows.

When to use Client Object Model?

We can use it from client machines where the entire SharePoint binaries are not available. A typical example would be from a Windows Form application in a client machine.

References

MSDN on Client Object Model
Technet Blog on Client Object Model

Summary

In this article we have seen an overview of the Client Object Model in SharePoint 2010. The source code attached contains various samples of working with the Client Object Model.