Why is list.GetItems pulling more fields than specified in my CamlQuery?

Question

I am trying to pull back just specific columns in a list using the .NET client object model. (i.e. using Microsoft.SharePoint.Client;)

This is the CamlQuery specifying just fields in the DefaultView ViewFields for the list

<View>
    <ViewFields>
        <FieldRef Name="LinkTitle" />
        <FieldRef Name="FoodName" />
    </ViewFields>
</View>

However, when I run the query using:

CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = "<View><ViewFields><FieldRef Name="LinkTitle" /><FieldRef Name="FoodName" /></ViewFields></View>";
ListItemCollection items = list.GetItems(camlQuery);
clientContext.Load(items);
clientContext.ExecuteQuery();

then each item's FieldValues has the following keys (columns) pulled back:

• FoodName
• MetaInfo
• _ModerationStatus
• _Level
• ID
• UniqueId
• owshiddenversion
• FSObjType
• Created_x0020_Date
• Created
• Title
• FileLeafRef
• Modified
• FileRef

Why is SharePoint pulling back these additional field values?

Answer 1

Update for client object model:

In client object model only specifying ViewFields is not enough. You need to combine it with a linq statement like this:

CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = "<View><Where><Eq>.<FieldRef Name='Country' /><Value Type='Text'>Belgium</Value></Eq></Where></View>";
ListItemCollection listItems = spList.GetItems(camlQuery);
clientContext.Load(listItems,
  items => items.Include(
  item => item.Id,
  item => item.DisplayName,
  item => item.HasUniqueRoleAssignments));
clientContext.ExecuteQuery();

Source: http://karinebosch.wordpress.com/2012/02/03/caml-and-the-client-object-model/

Answer 2

If you look here: http://karinebosch.wordpress.com/2012/02/03/caml-and-the-client-object-model/ under the section "ViewFields", you'll see the text: "But this also returns a number of system columns. If you really want to limit the columns returned to the columns you specify, you have to use a LINQ query within the Load method. The code looks as follows:"

Answer 3

This is a side note to the question... but it turns out that if you want non-field data such as EffectiveBasePermissions and HasUniqueRoleAssignments AS WELL AS item data from fields (e.g. Title, Modified by) you effectively call load on the listItems twice, as below:

clientContext.Load(listItems,
"Include(EffectiveBasePermissions, HasUniqueRoleAssignments)");
// Follow the statement above with this if you need special "fields" like 
//  HasUniqueRoleAssignments, EffectiveBasePermissions as well as the normal fields
clientContext.Load(listItems);