Cannot return an item's Author and Editor properties in CSOM

Question

I have a utility which makes updates without affecting the ModifiedBy/Editor field. Before any updates are made, I store the user value in one of two ways:

CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = _query;
ListItemCollection collListItem = list.GetItems(camlQuery);

context.Load(collListItem);
context.ExecuteQuery();

if (collListItem.Count > 0)
{
    foreach (ListItem item in collListItem)
    {       //both of these error out.. but only on this specific list
            object modifiedBy = item["Editor"];
            original_editor = item["Editor"] as FieldUserValue;

    }
}

This has been working in SP 2010 and SP 2013 for as long as the application has existed (~2 years), but I now have a list for which I am not able to use this. Other lists in the same site collection are updated just fine. The only difference with this list is that it has hundreds of fields (250-300). Is there an actual reason for why item["Editor"] is causing this error

"Microsoft.SharePoint.Client.PropertyOrFieldNotInitializedException" ?

Answer 1

I mentioned earlier that this list had hundreds of fields. That's actually the only thing that set this list apart from the rest. My CAML query simply added a scope of "RecursiveAll" along with my query. Because of the large number of fields, I needed to specify ViewFields. Nk SP was on the right track, but this is where I need to include the property instead.

Previous (not working on list with many fields) CAML:

<View Scope='RecursiveAll'>
    <Query>
        <Where><Eq><FieldRef Name='ID'/><Value Type='Number'>1</Value></Eq></Where>
    </Query>
</View>

Working CAML:

<View Scope='RecursiveAll'>
    <ViewFields>
        <FieldRef Name='Editor' />
        <FieldRef Name='Modified' />
    </ViewFields>
    <Query>
        <Where><Eq><FieldRef Name='ID'/><Value Type='Number'>1</Value></Eq></Where>
    </Query>
</View>

Answer 2

You have to include the property:

using (var clientContext = new ClientContext("http://yourSite/"))
{
    var oSite = clientContext.Site;
    clientContext.Load(oSite);
    var oWeb = oSite.OpenWeb("");
    clientContext.Load(oWeb, web => web.Lists);
    clientContext.ExecuteQuery();
    //get your list by index
    var list = oWeb.Lists[0];
    ListItemCollection itemsColl= list.GetItems(new CamlQuery());

    clientContext.Load(itemsColl,
        items => items.Include(
        item => item.Id,
        item => item["Editor"]));
    clientContext.ExecuteQuery();

    foreach (ListItem item in itemsColl)
    {
        Console.WriteLine((item["Editor"] as Microsoft.SharePoint.Client.FieldUserValue).LookupValue);
    }
}

How to: Retrieve List Items