使用自动映射器映射异步结果 [英] Map async result with automapper

问题描述

我们正在创建一个angularjs应用程序的Web.Api应用程序. Web.Api返回json结果.

We are createing a Web.Api application of a angularjs application. The Web.Api returns a json result.

第一步是获取数据:

    public List<DataItem>> GetData()
    {
        return Mapper.Map<List<DataItem>>(dataRepository.GetData());
    }

那就像一个魅力.然后，我们使数据存储异步，并更改为使用它的代码.

That worked like a charm. Then we made the data repo async and we changed to code to work with it.

    public List<DataItem>> GetData()
    {
        return Mapper.Map<List<DataItem>>(dataRepository.GetDataAsync().Result);
    }

仍然没有问题.现在我们要使Web.Api完全异步，所以我们将其更改为:

Stil no problems. Now we wanted to make my Web.Api full async awayt so we changed it to:

    public async Task<List<DataItem>> GetData()
    {
        return await Mapper.Map<Task<List<DataItem>>>(dataRepository.GetDataAsync());
    }

此时，Automapper感到困惑.首先，我们有以下映射规则: Mapper.CreateMap();

At this moment Automapper gets confused. First we had the following mapper rule: Mapper.CreateMap();

这一直有效，直到Web api方法变得完全异步为止.例外情况是，它缺少

This worked until the web api method became full async. The exception said it was missing a map from

 Task<ICollection<Data>> to Task<ICollection<DataItem>>.

映射器已更改为

Mapper.CreateMap<Task<List<Data>>, Task<List<DataItem>>>();

在验证配置时，它抱怨无法映射结果.我们应该如何配置映射?

When validating the configuration it complains that Result cannot be mapped. How should we configure the mappings?

推荐答案

您需要将获取的异步数据移出Map调用:

You need to move the async data fetch out of the Map call:

var data = await dataRepository.GetDataAsync();
return Mapper.Map<List<DataItem>>(data);

或者，您可以使用AutoMapper LINQ投影:

Alternatively, you can use AutoMapper LINQ projections:

var data = await dbContext.Data.ProjectTo<DataItem>().ToListAsync();

我不知道您的存储库是否直接公开IQueryable(我们不使用存储库).这些天，我们的应用几乎只使用第二个版本.

I don't know if your repository exposes IQueryable directly (we don't use repositories). Our apps use the second version pretty much exclusively these days.

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