Querying for File properties plus ListItemAllFields properties

Question

I'm trying to retrieve both a file's Id in its list, plus its ETag, using the following snippet;

using (var clientContext = new ClientContext(webUrl))
{
    var results = clientContext.Web.Lists
        .GetById(listId).RootFolder.Files;

    clientContext.Load(results, files => files
            .Include(file => file.ETag)
            .Include(file => file.ListItemAllFields.Id));

    clientContext.ExecuteQuery();
    foreach (var file in results)
    {
        Console.WriteLine(file.ETag + " " + file.ListItemAllFields.Id);
    }
}

However, I'm getting the following exception;

The query expression 'files => files.Include(new [] {file => file.ETag}).Include(new [] {file => Convert(file.ListItemAllFields.Id)})' is not supported.

Am I forming my query correctly? It seems that if I query for the ETag by itself, then the query works. And also, if I query for the ListItemAllFields.Id by itself, then the query works.

It's when they are both included in the one query that the failure occurs.

Answer 1

Managed to work this one out with a bit of trial and error. The correct form of the query is;

clientContext.Load(results,
    files => files.Include(file => file.ETag),
    files => files.Include(file => file.ListItemAllFields.Id));

Hopefully that's of some use to anyone else who encounters this issue.