CosmosDB generic OrderBy query or get last data first - sql

Question

I'm using the code from azure project, when CosmosDB is created first time. It has a nice generic GetItemsAsync method.
I have modified it a little to have following:
public static async Task<List<T>> GetItemsAsync(Expression<Func<T, bool>> predicate, int maxItemCount = -1)
{
IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId),
new FeedOptions { MaxItemCount = maxItemCount })
.Where(predicate)
.AsDocumentQuery();
List<T> results = new List<T>();
while (query.HasMoreResults)
{
results.AddRange(await query.ExecuteNextAsync<T>());
if (maxItemCount != -1)
{
break;
}
}
return results;
}
What I want to do is, in some calls to this method, I need to add OrderBy query. The problem is I have couple collections in same CosmosDB and fields are different. When I want to list one of the collections I just want to get latest ones.
So in this example, I actually send count as 50 so I will get only 50, but I also want to get recent ones. The above code returns oldest 50 as expected. Is there any solution this? I'm guessing there might be a way to get latest data first and when I call for 50, it would be latest 50 records.
Other thing I tried, was to create another method called GetItemsWithOrderByAsync and tried to give Expression>, but it requires so much modification in whole class to support TKey.

Answer 1

Ok, after playing around, I came up with the following as a solution. Created new method and:
public static async Task<List<T>> GetItemsWithOrderByAsync(Expression<Func<T, bool>> predicate, Expression<Func<T, object>> orderByPredicated, int maxItemCount = -1)
{
IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId),
new FeedOptions { MaxItemCount = maxItemCount }).
Where(predicate).
OrderByDescending(orderByPredicated).
AsDocumentQuery();
List<T> results = new List<T>();
while (query.HasMoreResults)
{
results.AddRange(await query.ExecuteNextAsync<T>());
if (maxItemCount != -1)
{
break;
}
}
return results;
}