如何在Azure移动应用服务中获取Cosmos Db数据

Question

I try to get Data in Cosmos Db using Azure Mobile App Service , I tried this documentation https://docs.microsoft.com/en-us/azure/cosmos-db/sql-api-dotnet-application#_Toc395637765 but I can't implement it from MVC to Azure Mobile App Service , I'm still very new in ASP and don't realy understand all the function, in this Documentation they use this to get the data from it.

public ActionResult Index()
{
    return View();
}

 [ActionName("Index")]
 public async Task<ActionResult> IndexAsync()
 {
     var items = await DocumentDBRepository<Item>.GetItemsAsync(d => !d.Completed);
     return View(items);
 } 

But because my ASP.NET is not MVC so I can't use ActionResult (my App Service will not have view) and that what make it confusing for me, I don't know how to return the task, and ussualy I'm using StreamReader to return the data but it says my Task doesn't contain StreamReader

This is the DocumentDB class which handle the GetData :

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

namespace gumilangService.Controllers
{
    public static class DocumentDBRepository<T> where T : class
    {
        private static readonly string DatabaseId = ConfigurationManager.AppSettings["database"];
        private static readonly string CollectionId = ConfigurationManager.AppSettings["collection"];
        private static DocumentClient client;

        public static void Initialize()
        {
            client = new DocumentClient(new Uri(ConfigurationManager.AppSettings["endpoint"]), ConfigurationManager.AppSettings["authKey"]);            
        }

        public static async Task<IEnumerable<T>> GetItemsAsync(Expression<Func<T, string>> predicate)
        {
            IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
                UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId))
               // .Where(predicate)
                .AsDocumentQuery();

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

            return results;
        }  
    }
}

And this is my Controller so far:

public  string Get()
{
    var items =  DocumentDBRepository<MyCollection>.GetItemsAsync(d => d.Id);
    /*  using (var streamReader = new StreamReader(items.GetResponseStream()))
              {
                  var result = streamReader.ReadToEnd();
                  return result;
              }
    */
    return items.ToString();
    //return "Hello";    
}

And it return this instead the data:

System.Threading.Tasks.Task`1[System.Collections.Generic.IEnumerable`1[gumilangService.DataObjects.MyCollection]]

Any idea how to implement this and get the data when I try it in Postman ?

Answer 1

You need to go back a bit further.

Your Get() method in the "controller" returns a string - it needs to return the actual data. ASP will serialize that data into a string using either XML or JSON.

public MyItem Get(string id){
    Item item = DocumentDBRepository<MyItem>.Get(x => x.Id == id);
    return item; // separate line so you can put a breakpoint here and look
}

You used an async method

var items =  DocumentDBRepository<MyCollection>.GetItemsAsync(d => d.Id);

which returns Task. The correct way to call async methods is to make your own method async by replacing its return type with "async Task" and adding "await" before all async calls to other methods:

 var items =  await DocumentDBRepository<MyCollection>.GetItemsAsync(d => d.Id);

This is likely not the only issue... I strongly recommend that you download some sample project and understand how it works.