我一般来说是EF,Linq和C#的新手,但我坚持开发以下对象。我不能将数据映射到这样的结构中:
Id,
Actions [
Action1,
Action2,
Action3
]
我有2个这样的DTO类:
public class TestDTO
{
public int TestId { get; set; }
public TestDTO2[] Actions { get; set; }
}
和
public class TestDTO2
{
public int TestActionId { get; set; }
public DateTime? StartDate { get; set; }
...
}
我已经将对DB的调用分离到名为BusinessLogic的文件中,我正在这样做:
public IQueryable<TestDTO> GetNested(Filter filter)
{
var query =
from a in db.Table1.AsQueryable()
select new TestDTO
{
TestId = a.Id,
Actions = (
from b in db.Table2.AsQueryable()
where a.Id == b.TestId
select new TestDTO2
{
TestActionId = b.TestActionId,
StartDate = b.StartDate
}
).ToArray()
};
return query;
}
我收到以下错误:
LINQ to Entities无法识别方法'Project.Core.Models.TestDTO2 [] ToArrayTestDTO2',并且该方法无法转换为商店表达式。
您不能完全执行此查询,最好进行两个简单的查询,然后在客户端处理它们的结果:
var main = db.Table1.Select(x => new { x.Id, x.Title }).ToList();
var mainIds = main.Select(x => x.Id).ToList();
var actions = db.Table2.Where(x => mainIds.Contains(x.TestId)).Select(x => new
{
x.TestId,
x.TestActionId,
x.StartDate
}).ToList();
var result = main.Select(x => {
var actions = actions.Where(y => y.TestId == x.Id).Select(y => new TestDTO2
{
TestActionId = y.TestActionId,
StartDate = y.StartDate
}).ToArray();
return new TestDTO
{
TestId = x.Id,
Title = x.Title,
Actions = actions.Length == 0 ? null : actions
};
}).ToList();
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