Async GetAwaiter() 抛出一个奇怪的异常

Question

下面我粘贴了一些代码。在正文的第一行，我调用了一个等待调用 Task<IEnumerable<SkuGcn>> GetSkuGcnList(); 在最后一行，在 mapPromise.GetAwaiter() 中，它在获取结果时抛出此异常：

An exception of type 'System.IO.FileNotFoundException' occurred in System.Private.CoreLib.ni.dll but was not handled in user code

Additional information: Could not load file or assembly 'System.Runtime.Serialization.Xml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.

我知道 GetSkuGcnList() 调用正在调用我的服务，因为我可以设置一个断点并在调用时中断它。然后服务好像return.

此代码在 ASP.NET 5 RC1 中运行良好，但在 ASP.Net Core 1.0 版本中效果不佳。

任何帮助将不胜感激！

        public ProductItemsCacheStore(IItemsProductCacheRepository itemsRepo, IProductAvailabilityPricing proxyGoliathApi,
        IProductItemListRepo itemsListsRepo, IItemPricesCacheRepo itemPricesRepo)
        {
            var mapPromise = proxyGoliathApi.GetSkuGcnList();
            _items = itemsRepo.GetAllProductOrderListForCache();
            _itemsLists = itemsListsRepo.GetItemListsForCache();
            _priceZones = itemPricesRepo.GetAllPriceZonesAndItemPrices();
            MergeProductsWithGcn(_items, mapPromise.GetAwaiter().GetResult());
        }

我的 project.json 看起来像这样：

{
  "version": "1.0.0-alpha.1",
  "description": "AvailabilityPricingClient Class Library",
  "authors": [ "irving.lennert" ],
  "packOptions": {
    "tags": [ "" ],
    "projectUrl": "",
    "licenseUrl": ""
  },

  "tooling": {
    "defaultNamespace": "AvailabilityPricingClient"
  },

  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.0",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Logging": "1.0.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.AspNet.WebApi.Client": "5.2.3"
  },

  "frameworks": {
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }
  }
}

GetSkuGcnList()的实现是这样的：

    public async Task<IEnumerable<SkuGcn>> GetSkuGcnList()
    {
        HttpResponseMessage response = _client.GetAsync("/api/skuGcnList").Result;

        if (response.IsSuccessStatusCode)
        {
            var skuGcns = await response.Content.ReadAsAsync<IEnumerable<SkuGcn>>();
            return skuGcns;
        }

        return null;
    }

Answer 1

正如@DaniDev 在评论中提到的，不建议混合使用同步和异步代码。关于此主题的规范文章是 Stephen Cleary 的 Don't Block on Async Code.

让你的代码异步有点棘手，因为你在构造函数中调用异步操作，constructors can't be async。

重组代码的一种方法是拆分构造函数（依赖注入）和初始化（异步调用）代码：

public class ProductItemsCacheStore
{
    private readonly IItemsProductCacheRepository _itemsProductCacheRepo;
    private readonly IProductAvailabilityPricing _productAvailabilityPricing;
    private readonly IProductItemListRepo _productItemListRepo;
    private readonly IItemsPricesCacheRepo _itemsPricesCacheRepo;

    private bool _initialized = false;

    public ProductItemsCacheStore(
        IItemsProductCacheRepository itemsRepo,
        IProductAvailabilityPricing proxyGoliathApi,
        IProductItemListRepo itemsListsRepo,
        IItemPricesCacheRepo itemPricesRepo)
    {
        _itemsProductCacheRepo = itemsRepo;
        _productAvailabilityPricing = proxyGoliathApi;
        _productItemListRepo = itemsListsRepo;
        _itemsPricesCacheRepo = itemsPricesRepo
    }

    public async Task Initialize()
    {
        // Could possibly move these to the constructor as well
        var _items = itemsRepo.GetAllProductOrderListForCache();
        var _itemsLists = itemsListsRepo.GetItemListsForCache();
        var _priceZones = itemPricesRepo.GetAllPriceZonesAndItemPrices();

        MergeProductsWithGcn(_items, await _productAvailabilityPricing.GetSkuGcnList());

        _initialized = true;
    }
}

您的消费代码（无论您之前在哪里构建 new ProductItemsCacheStore(...)）现在看起来像：

var productItemsCacheStore = new ProductItemsCacheStore(/* dependencies */);
await productItemsCacheStore.Initialize();

当然，这意味着您的消费代码也必须是异步的。这是 .

Answer 2

我确定我正在调用的程序集在 ASP.Net 核心版本中无法正常工作。如果你看上面的 project.json 就是这一行：

"Microsoft.AspNet.WebApi.Client": "5.2.3"

我已将该行更改为此行：

"System.Net.Http": "4.1.0"

这个程序集没有公开相同的 API 所以我不得不将我的实现代码更改为：

    public async Task<IEnumerable<SkuGcn>> GetSkuGcnList()
    {
        HttpResponseMessage response = _client.GetAsync("/api/skuGcnList").Result;

        if (response.IsSuccessStatusCode)
        {
            var skuGcns = await response.Content.ReadAsStringAsync()
                .ContinueWith<IEnumerable<SkuGcn>>(getTask =>
                {
                    return JsonConvert.DeserializeObject<IEnumerable<SkuGcn>>(getTask.Result);
                });
            return skuGcns;
        }

        return null;
    }

此解决方案运行良好。重要的是要注意我在 post 上也遇到了同样的问题，它们有点复杂，所以我会提供另一个我打的电话 post 给任何感兴趣的人。

    public async Task<IEnumerable<Availablity>> GetAvailabilityBySkuList(IEnumerable<string> skuList)
    {
        var output = JsonConvert.SerializeObject(skuList);
        HttpContent contentPost = new StringContent(output, System.Text.Encoding.UTF8, "application/json");
        HttpResponseMessage response = _client.PostAsync("/api/availabilityBySkuList", contentPost).Result;

        if (response.IsSuccessStatusCode)
        {
            var avail = await response.Content.ReadAsStringAsync()
                .ContinueWith<IEnumerable<Availablity>>(postTask =>
                {
                    return JsonConvert.DeserializeObject<IEnumerable<Availablity>>(postTask.Result);
                });
            return avail;
        }

        return null;
    }

感谢所有的贡献！

Async GetAwaiter() 抛出一个奇怪的异常

Async GetAwaiter() throwing an odd exception

c#

asp.net

asp.net-core

.net-core

asp.net-core-1.0