LINQ project（）以在LINQ IQueryable中从数据实体自动映射到业务实体？

Question

我不确定这是否可能。

一些要求

• 我们的查询一直都是IQueryable。
• 通过OData传递的所有参数
• 实体和业务实体是分开的，我们的查询应仅
• 返回业务实体，而不是数据实体

这是我们正在尝试做的

var query = from mpg in this.markingPeriodGroupRepository.GetAll()
            join mp in this.markingPeriodRepository.GetAll().Include(x => x.SchoolMarkingPeriods) 
                on mpg.MarkingPeriodGroupID equals mp.MarkingPeriodGroupID
            select new MarkingPeriodTerm
            {
                MarkingPeriodGroupID = mpg.MarkingPeriodGroupID,
                MarkingPeriodGroupName = mpg.MarkingPeriodGroupName,
                SchoolMarkingPeriods = mp.SchoolMarkingPeriods.AsQueryable()
                    .Project().To<SchoolMarkingPeriod>(null).ToList()
            };

在运行时，我们收到此错误：

LINQ to Entities无法识别方法'System.Linq.IQueryable 1[NHA.App.Core.v2.Business.Models.SchoolMarkingPeriod] To[SchoolMarkingPeriod](System.Collections.Generic.IDictionary 2 [System.String，System。 Object]）方法，并且该方法无法转换为商店表达式。

是否可以在此IQueryable中自动映射此属性？

Answer 1

在您的查询中，选择一个匿名类型，并且不执行Project方法。

var query = from mpg in this.markingPeriodGroupRepository.GetAll()
            join mp in this.markingPeriodRepository.GetAll().Include(x => x.SchoolMarkingPeriods)
                on mpg.MarkingPeriodGroupID equals mp.MarkingPeriodGroupID
            select new //Here we are selecting an anonymous type
            {
                MarkingPeriodGroupID = mpg.MarkingPeriodGroupID,
                MarkingPeriodGroupName = mpg.MarkingPeriodGroupName,
                SchoolMarkingPeriods = mp.SchoolMarkingPeriods   
            };

然后，执行查询后，我们可以使用Project方法。

var result = query
    .ToList() //This will actually execute the query.
    .Select(x => new MarkingPeriodTerm()
    {
        MarkingPeriodGroupID = x.MarkingPeriodGroupID,
        MarkingPeriodGroupName = x.MarkingPeriodGroupName,
        SchoolMarkingPeriods = x.SchoolMarkingPeriods.Project().To<SchoolMarkingPeriod>(null).ToList() //Here we are executing the Project method on in-memory data
    });