异步方法有时不执行

Question

我有使用异步方法的WebApi控制器Post：

public class WebApiController : ApiController
{
 public async Task<HttpResponseMessage> Post(HttpRequestMessage request)
    {
        try
        {
            string json = await request.Content.ReadAsStringAsync();
            var model = JsonConvert.DeserializeObject<TModel>(json);
            var newEntity = Mapper.Map<TEntity>(model);
            var newEntityVersion = Mapper.Map<TEntityVersion>(model);
            var result = await CurrentRepository.AddAsync(newEntity, newEntityVersion);

            return CreateResponse(result, "DefaultApiPost");
        }
        catch (Exception e)
        {
            Logger.Error("Post in " + ControllerName, e);

            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, e);
        }
    }
}

AddAsync方法如下：

public virtual async Task<TEntity> AddAsync(TEntity entity, TEntityVersion version)
{
 await DatabaseContext.SaveChangesAsync();
 return entity;
}

当我使用HttpClient调用Post方法时，我可以输入AddAsync方法：

client.PostAsync(requestUri, content).Result.Content.ReadAsStringAsync().Result;

但是当我使用WebApi控制器显式调用Post方法时，我无法输入AddAsync方法，只需跳过它：/：

 var product = FakeProduct();

        var newEntity = Mapper.Map<ProductEntity>(product);
        var newEntityVersion = Mapper.Map<ProductVersionEntity>(product);

        productRepository.AddAsync(newEntity, newEntityVersion).Returns(Task.FromResult<ProductEntity>(newEntity));


        var content = JsonConvert.SerializeObject(Product);

        var request = new HttpRequestMessage(HttpMethod.Post, "http://localhost:8888/api/Product/")
          {
              Content = new StringContent(content),
          };

        var webApiController = FakeWebApiControllerWithPostRoute();

        var result = await webApiController.Post(request);

        Assert.AreEqual(HttpStatusCode.Created, result.StatusCode);

知道为什么不执行此方法？