Update list item or change item value using Client Object Model

"Client" in the namespace.  For example, in the server object model you have:
Microsoft.SharePoint.SPSite
Microsoft.SharePoint.SPWeb
Microsoft.SharePoint.SPList

In the client object model you have:
Microsoft.SharePoint.Client.Site
Microsoft.SharePoint.Client.Web
Microsoft.SharePoint.Client.List


NameSpace:


Microsoft.SharePoint.Client.dll
Microsoft.SharePoint.Client.Runtime.dll


Example Code:

ClientContext context = new ClientContext("http://peakfinders.com");

Web web = context.Web;

List list = web.Lists.GetByTitle("yourlistname");

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"] = "Complete";
item.Update();

context.ExecuteQuery();