DocumentDBRepository.cs

namespace todo
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Linq.Expressions;
    using System.Threading.Tasks;
    using Microsoft.Azure.Documents;
    using Microsoft.Azure.Documents.Client;
    using Microsoft.Azure.Documents.Linq;
    using Microsoft.Extensions.Configuration;

    public class DocumentDBRepository<T> : IDocumentDBRepository<T> where T : class
    {
       
        private readonly string Endpoint;
        private readonly string Key;
        private readonly string DatabaseId;
        private readonly string CollectionId;

        private DocumentClient client;

        public DocumentDBRepository(IConfiguration configuration)
        {
            Endpoint = configuration["CosmosDB:AccountEndpoint"];
            Key = configuration["CosmosDB:AccountKeys"];
            DatabaseId = configuration["CosmosDB:Database"];
            CollectionId = configuration["CosmosDB:Collection"];

            var connectionPolicy = new ConnectionPolicy
            {
                ConnectionMode = ConnectionMode.Gateway,
                ConnectionProtocol = Protocol.Https
            };

            var usConnectionPolicy = connectionPolicy;
            //Choose your preferred location
            usConnectionPolicy.PreferredLocations.Add(LocationNames.NorthEurope);
            usConnectionPolicy.PreferredLocations.Add(LocationNames.JapanEast);

            this.client = new DocumentClient(new Uri(Endpoint), Key, usConnectionPolicy);
            client.OpenAsync().Wait();
            CreateDatabaseIfNotExistsAsync().Wait();
            CreateCollectionIfNotExistsAsync().Wait();
        }

        public async Task<T> GetItemAsync(string id)
        {
            try
            {
                Document document = await client.ReadDocumentAsync(UriFactory.CreateDocumentUri(DatabaseId, CollectionId, id));
                return (T)(dynamic)document;
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    return null;
                }
                else
                {
                    throw;
                }
            }
        }

        public async Task<IEnumerable<T>> GetItemsAsync(Expression<Func<T, bool>> predicate)
        {
            IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
                UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId),
                new FeedOptions { MaxItemCount = -1 })
                .Where(predicate)
                .AsDocumentQuery();

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

            return results;
        }

        public async Task<Document> CreateItemAsync(T item)
        {
            return await client.CreateDocumentAsync(UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId), item);
        }

        public async Task<Document> UpdateItemAsync(string id, T item)
        {
            return await client.ReplaceDocumentAsync(UriFactory.CreateDocumentUri(DatabaseId, CollectionId, id), item);
        }

        public async Task DeleteItemAsync(string id)
        {
            await client.DeleteDocumentAsync(UriFactory.CreateDocumentUri(DatabaseId, CollectionId, id));
        }

        private async Task CreateDatabaseIfNotExistsAsync()
        {
            try
            {
                await client.ReadDatabaseAsync(UriFactory.CreateDatabaseUri(DatabaseId));
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    await client.CreateDatabaseAsync(new Database { Id = DatabaseId });
                }
                else
                {
                    throw;
                }
            }
        }

        private async Task CreateCollectionIfNotExistsAsync()
        {
            try
            {
                await client.ReadDocumentCollectionAsync(UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId));
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    await client.CreateDocumentCollectionAsync(
                        UriFactory.CreateDatabaseUri(DatabaseId),
                        new DocumentCollection { Id = CollectionId },
                        new RequestOptions { OfferThroughput = 1000 });
                }
                else
                {
                    throw;
                }
            }
        }
    }
}