Question

以下Web API端点仍然出现以下错误：

“在此前提下开始第二次操作异步操作完成。“

由于我使用.ToListAsync和实体框架返回的数据，我假设问题是var user行阻塞。

如何使该部分同步？

[Route("Retailers/{search}")]
[HttpGet]
public Task<List<Lookup>> Retailers(string search)
{
    var user = UserManager.FindById(User.Identity.GetUserId());
    Guid userId = Guid.Parse(user.Id);

    var companies = _unitOfWork.GetRepository<Company>().GetAll().Where(c => c.CompanyType == CompanyType.Retail && 
                (c.UserID == null || c.UserID == userId) && c.CompanyName.StartsWith(search)).Take(5)
                .Select(x => new Lookup { Id = x.Id, Name = x.CompanyName }).ToListAsync();

    return companies;
}

Answer 1

您遗漏了async和await个关键字。

将async添加到方法签名。
将await添加到您对_unitOfWork.GetRepository...ToListAsync()

代码：

[Route("Retailers/{search}")]
[HttpGet]
public async Task<List<Lookup>> Retailers(string search)
{
    var user = UserManager.FindById(User.Identity.GetUserId());
    Guid userId = Guid.Parse(user.Id);

    var companies = await _unitOfWork.GetRepository<Company>().GetAll().Where(c => c.CompanyType == CompanyType.Retail && 
                (c.UserID == null || c.UserID == userId) && c.CompanyName.StartsWith(search)).Take(5)
                .Select(x => new Lookup { Id = x.Id, Name = x.CompanyName }).ToListAsync();

    return companies;
}

作为参考，这里是异步编程的一个很好的链接：Asynchronous Programming with Async and Await。

异步Web API端点

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