Querying DocumentDB for a list of propertiers using Linq's Select - azure

Question

Using Azure's DocumentDb and the .NET API, I have the following method which works great for retrieving lists of entire documents:
public async Task<IEnumerable<T>> GetItemsAsync<T>(Expression<Func<T, bool>> predicate)
{
IDocumentQuery<T> query = _Client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(_DatabaseId, _Collection),
new FeedOptions { MaxItemCount = -1 })
.Where(predicate)
.AsDocumentQuery();
List<T> results = new List<T>();
while (query.HasMoreResults)
{
var item = await query.ExecuteNextAsync<T>();
results.AddRange(item);
}
return results;
}
Now, I don't always want to return the entire document (especially considering the DocumentDb RU pricing model), so I thought I should be able to add a .Select projection like so:
public async Task<List<TResult>> GetItemsAsync<T, TResult>(Expression<Func<T, bool>> predicate, Expression<Func<T, TResult>> select)
{
IDocumentQuery<TResult> query = _Client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(_DatabaseId, _Collection),
new FeedOptions { MaxItemCount = -1 })
.Where(predicate)
.Select(select)
.AsDocumentQuery();
List<TResult> results = new List<TResult>();
while (query.HasMoreResults)
{
var item = await query.ExecuteNextAsync<TResult>();
results.AddRange(item);
}
return results;
}
Usage:
var rez = await _docs.GetItemsAsync<ApolloAssetDoc, Guid?>(x => x.MyVal == 5, x => x.ID);
But the second method always return 0 results. Obviously I'm barking up the wrong tree.
Any idea what the correct way to return a list of either dynamic objects for queries where more than one property is selected (eg "SELECT d.id, d.MyVal FROM Items d WHERE d.DocType=0")or a simple list where only a single property is selected (eg "SELECT d.id FROM Items d WHERE d.DocType=0")?

Answer 1

I could repro the issue, if there is no [JsonProperty(PropertyName = "id")] for ID property in the entity Class. If it is not included, please have a try to use the following code:
public class ApolloAssetDoc
{
[JsonProperty(PropertyName = "id")]
public Guid ID { get; set; }
public string MyVal { get; set; }
}
Note: The field is case sensitive.