[我正在调用api,然后将该响应反序列化为列表,当我随后尝试对新列表进行响应时:
public async Task<IEnumerable<RoadDto>> GetRoadStatusDetail()
{
List<Road> road = await CallApi();
return road
.Select(x => _mapper.Map(x));
}
private async Task<List<Road>> CallApi()
{
HttpClient client = new HttpClient();
client.BaseAddress = new Uri(baseURL);
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage res = await client.GetAsync(baseURL);
if (res.IsSuccessStatusCode)
{
var roadResponse = res.Content.ReadAsStringAsync().Result;
var road = JsonConvert.DeserializeObject<List<Road>>(roadResponse);
return road;
}
return null;
}
我没有使用自动映射器,而是使用了这种通用方法:
public interface IMapToNew<in TIn, out TOut>
{
TOut Map(TIn model);
}
我得到的错误是
System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
_mapper was null.
我不确定为什么它会为null,我在这里创建了一个应处理该问题的映射类?
public class RoadToRoadDtoMapper : IMapToNew<Road, RoadDto>
{
public RoadDto Map(Road model)
{
return new RoadDto
{
DisplayName = model?.DisplayName,
StatusSeverity = model?.StatusSeverity,
StatusSeverityDescription = model?.StatusSeverityDescription
};
}
}
_mapper
变量为null,因为错误状态。 DI您的映射器接口到您的控制器: