ASP.NET MVC WebAPI从Async任务中创建ViewModel

Question

我使用 ASP.NET MVC WebAPI 编写 Web 应用程序，我想将当前的同步代码转换为异步代码以进行优化。问题是我用从存储库中获取的多个对象填充 ViewModel。这些来自存储库的调用应该是异步的。

假设我有关于此接口的存储库调用的签名

public interface ICompanyRepository
{
    IEnumerable<Company> GetCompanies();
    IEnumerable<Address> GetAddresses();
}

ViewModel 定义

public class CompaniesFullViewModel
{
    public IEnumerable<Company> Companies { get; set; }
    public IEnumerable<Address> Addresses { get; set; }
}

和控制器：

public class CompanyController
{
    public readonly ICompanyRepository Repository { get; private set; }

    public CompanyController(IRepository repository)
    {
        Repository = repository;
    }

    [ResponseType(typeof(CompaniesFullViewModel))]
    public HttpResponseMessage Get()
    {
        var companies = Repository.GetCompanies();
        var addresses = Repository.GetAddresses();

        HttpStatusCode statusCode = companies.Any()
             ? HttpStatusCode.OK
             : HttpStatusCode.PartialContent;

        return
            Request.CreateResponse(
                statusCode,
                new CompaniesFullViewModel
                {
                    Companies = companies,
                    Addresses = addresses
                });
    }
}

此外，我已经对控制器进行了测试：

[TestClass]
public sealed class CompanyTestController : BaseTestController
{
    #region Fields

    private static Mock<ICompanyRepository> _repositoryMock;
    private static CompanyController _controller;

    #endregion

    [ClassInitialize]
    public static void Initialize(TestContext testContext)
    {
        // Mock repository
        _repositoryMock = new Mock<ICompanyRepository>();
        DependencyResolver.Default.Container.RegisterInstance(_repositoryMock.Object);

        // Create controller
        _controller =
            DependencyResolver.Default.Container.Resolve<CompanyController>();

        // Init request
        _controller.Request = new HttpRequestMessage();
        _controller.Request.SetConfiguration(new HttpConfiguration());
    }

    [ClassCleanup]
    public static void Cleanup()
    {
        _controller.Dispose();
    }

    [TestMethod]
    public void Get_ActionExecutes_ReturnsEmptyCompaniesViewModel()
    {
        var companies = new List<Company>();
        var addresses = new List<Address>();

        // Setup fake method
        _repositoryMock
            .Setup(c => c.GetCompanies())
            .Returns(companies);
        _repositoryMock
            .Setup(c => c.GetAddresses())
            .Returns(addresses);

        // Execute action
        var response = _controller.Get();

        // Check the response
        Assert.AreEqual(HttpStatusCode.PartialContent, response.StatusCode);
    }
}

如果存储库是异步的并且签名如下所示，我如何将控制器转换为异步：

public interface ICompanyRepository
{
    Task<IEnumerable<Company>> GetCompaniesAsync();
    Task<IEnumerable<Address>> GetAddressesAsync();
}

Answer 1

您需要做的是将Controller 操作也更改为async，并将返回类型更改为Task<>。然后，您可以等待异步存储库调用：

[ResponseType(typeof(CompaniesFullViewModel))]
public async Task<HttpResponseMessage> Get() // async keyword. 
{
    var companies = await Repository.GetCompaniesAsync(); // await
    var addresses = await Repository.GetAddressesAsync(); // await

    HttpStatusCode statusCode = companies.Any()
         ? HttpStatusCode.OK
         : HttpStatusCode.PartialContent;

    return
        Request.CreateResponse(
            statusCode,
            new CompaniesFullViewModel
            {
                Companies = companies,
                Addresses = addresses
            });
}

按照惯例，您也可以将控制器操作的名称更改为以Async 结尾，尽管如果您使用 RESTful 约定和/或路由属性，控制器操作的实际名称并不重要.

测试

我使用XUnit和NUnit，但似乎MSTest也支持asynchronous methods的测试，而且Moq还提供Async版本的设置：

[Test]
public async Task Get_ActionExecutes_ReturnsEmptyCompaniesViewModel() // async Task
{
    var companies = new List<Company>();
    var addresses = new List<Address>();

    // Setup fake method
    _repositoryMock
        .Setup(c => c.GetCompaniesAsync())
        .ReturnsAsync(companies); // Async
    _repositoryMock
        .Setup(c => c.GetAddressesAsync())
        .ReturnsAsync(addresses); // Async

    // Execute action
    var response = await _controller.Get(); // Await

    // Check the response
    Assert.AreEqual(HttpStatusCode.PartialContent, response.StatusCode);
    _repositoryMock.Verify(m => m.GetAddressesAsync(), Times.Once);
    _repositoryMock.Verify(m => m.GetCompaniesAsync(), Times.Once);
}

顺便说一句，您似乎正在使用 Setter 依赖注入。另一种方法是使用构造函数注入，它的好处是确保类始终处于有效状态（即在等待设置依赖项时没有瞬态状态）。这也允许将依赖项（在本例中为您的存储库）设为readonly。