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我有一个项目实体，它具有导航属性 ProjectNumbers、Addresses、Contacts 和 BBLInfos。我试图只选择每个导航属性的某些字段并将它们存储在视图模型中。

视图模型如下所示：

public class PropertyInfoViewModel
{
    public ProjectViewModel Project { get; set; }
    public IQueryable<ProjectNumberViewModel> ProjectNumbers { get; set; }
    public IQueryable<AddressViewModel> Addresses { get; set; }
    public IQueryable<BBLInfoViewModel> BBLInfos { get; set; }
    public IQueryable<ContactsViewModel> Contacts { get; set; }
}

对项目 DbSet 调用 .Include 不起作用，因为它包含整个相关实体。

我能够通过分别对每个相关表进行查询并选择其 ProjectId 与项目匹配的实体来使其工作，但这需要 4 个单独的表查询。有没有更有效的方法来获取相关实体，而只从相关实体中选择几列？

这就是我目前正在做的事情：

 PropertyInfoViewModel model = PropertyInfoViewModel.ViewModelSelector().Invoke(
    new Repository<Project>(epicContext).Get(id),
    new Repository<ProjectNumber>(epicContext).Get(projectNumber => projectNumber.ProjectId == id),
    new Repository<Address>(epicContext).Get(address => address.ProjectId == id),
    new Repository<BBLInfo>(epicContext).Get(bblInfo => bblInfo.ProjectId == id),
    new Repository<Contact>(epicContext).Get(contact => contact.ProjectId == id)

然后 ViewModelSelector 只选择需要的字段：

public class PropertyInfoViewModel
{
    public static Func<Project, IQueryable<ProjectNumber>, IQueryable<Address>, IQueryable<BBLInfo>, IQueryable<Contact>, PropertyInfoViewModel> ViewModelSelector()
    {
        return (project, projectNumbers, addresses, bblInfos, contacts, projectInfo) =>
            new PropertyInfoViewModel()
            {
                Project = project,
                ProjectNumbers = projectNumbers.Select(ProjectNumberViewModel.ViewModelSelector()).AsQueryable(),
                Addresss = addresses.Select(AddressViewModel.ViewModelSelector()).AsQueryable(),
                BBLInfos = bblInfos.Select(BBLInfoViewModel.ViewModelSelector()).AsQueryable(),
                Contacts = contacts.Select(ContactViewModel.ViewModelSelector()).AsQueryable(),
            };
    }

ViewModelSelector 函数是这样的，所以我只需要编写一次 linq 查询的“.select”部分，然后我就可以重用它们。内部 ViewModelSelector 方法仅选择特定字段，如下所示：

public static Func<Address, AddressViewModel> ViewModelSelector()
    {
        return address => new AddressViewModel()
        {
            ProjectId = address.ProjectId,
            AddressId = address.AddressId,
            StreetNumber = address.StreetNumber,
            StreetName = address.StreetName,
            ZipCode = address.ZipCode
        };
    }

谢谢！

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