DocDBRepo.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.Azure.Documents;
using Microsoft.Azure.Documents.Client;
using Microsoft.Azure.Documents.Linq;
using System.Configuration;
using System.Linq.Expressions;
using System.Threading.Tasks;
using UltraReadingWeb.Common;

namespace UltraReadingWeb.Common
{
    public static class DocDBRepo<T> where T : class
    {   
        private static DocumentClient client;

        public static void Initialize()
        {
            client = new DocumentClient(new Uri(Constants.EndPoint)
                , Constants.AuthKey);
            CreateDatabaseIfNotExistsAsync().Wait();
            CreateCollectionIfNotExistsAsync().Wait();
        }
        private static async Task CreateDatabaseIfNotExistsAsync()
        {
            try
            {
                await client.ReadDatabaseAsync(UriFactory.CreateDatabaseUri(Constants.DatabaseId));
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    await client.CreateDatabaseAsync(new Database { Id = Constants.DatabaseId });
                }
                else
                {
                    throw;
                }
            }
        }

        private static async Task CreateCollectionIfNotExistsAsync()
        {
            try
            {
                await client.ReadDocumentCollectionAsync(UriFactory.CreateDocumentCollectionUri(Constants.DatabaseId, Constants.CollectionId));
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    await client.CreateDocumentCollectionAsync(
                        UriFactory.CreateDatabaseUri(Constants.DatabaseId),
                        new DocumentCollection { Id = Constants.CollectionId },
                        new RequestOptions { OfferThroughput = 1000 });
                }
                else
                {
                    throw;
                }
            }
        }
        public static async Task<IEnumerable<T>> GetItemsAsync(Expression<Func<T, bool>> predicate)
        {
            IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
                UriFactory.CreateDocumentCollectionUri(Constants.DatabaseId, Constants.CollectionId))
                .Where(predicate)
                .AsDocumentQuery();

            List<T> results = new List<T>();
            while (query.HasMoreResults)
            {
                results.AddRange(await query.ExecuteNextAsync<T>());
            }

            return results;
        }
        
    }
}