动态表达式 LINQ Select - Select 来自嵌套集合的许多

Question

将此示例 class 结构考虑在内 -

public class Apprentice
{
    public Guid Id { get; set; }
    public string GivenName { get; set; }
    public string FamilyName { get; set; }
    public virtual ICollection<ApprenticeAddress> Addresses { get; set; }
}

public class ApprenticeAddress
{
    public Guid Id { get; set; }
    public Guid ApprenticeId { get; set; }
    public virtual Apprentice Apprentice { get; set; }
    public string AddressLine1 { get; set; }
    public string AddressLine2 { get; set; }
    public string Town { get; set; }
    public Guid CountyId { get; set; }
    public virtual County County { get; set; }
    public string PostCode { get; set; }
    public bool IsPrimaryAddress { get; set; }
    public Guid AddressTypeId { get; set; }
    public virtual AddressType AddressType { get; set; }
}

根据上述文档和提供的示例 class 结构，我一直在努力编译动态 select 或 selecting 运行时未知的随机属性。我一直遇到的主要问题是 select 说 AddressLine1 属性链接到返回学徒的任何地址。

此示例 LINQ select 将执行我需要执行的操作，但任何人都可以帮助将其转换为数据对象初始化字符串吗？

var r = repo.GetAll().ToList().Select(x =>
        new
        {
            x.FamilyName,
            addresses = x.Addresses.SelectMany(y => y.AddressLine1)
        });

更新

如果我使用下面的代码和传递给 Select 扩展方法的数据对象初始化字符串，我会得到我想要的匿名对象 -

var whereTxt = "Active";
var selectTxt = "new (GivenName AS GivenName,FamilyName AS FamilyName)";
var repo = Storage.DataContext.GetRepository<Apprentice>();
return repo.GetAll().Where(whereTxt).Select(selectTxt).AsQueryable();

我遇到的问题是确定从嵌套集合中检索特定属性（在运行时未知）的语法

Answer 1

这可以使用 System.Linq.Dynamic.Core 轻松完成：

var data = new[]
{
    new Apprentice { FamilyName = "f", Addresses = new [] { new ApprenticeAddress { AddressLine1 = "address x" }, new ApprenticeAddress { AddressLine1 = "address y" } } }
}.AsQueryable();

var result = data.Select(x => new { x.FamilyName, Addresses = x.Addresses.Select(y => y.AddressLine1) });
Console.WriteLine("result: " + JsonConvert.SerializeObject(result, Formatting.Indented));

var resultDynamic = data.Select("new (FamilyName as FamilyName, Addresses.Select(AddressLine1) as Addresses)");
Console.WriteLine("resultDynamic: " + JsonConvert.SerializeObject(resultDynamic, Formatting.Indented));

有关完整的工作示例，请参阅 https://github.com/StefH/System.Linq.Dynamic.Core.TestApps

中的 ConsoleApp2

注意Addresses.SelectMany(y => y.AddressLine1)是错误的，这里是从地址中选择字符。

动态表达式 LINQ Select - Select 来自嵌套集合的许多

Dynamic Expressions LINQ Select - SelectMany from nested collection

c#

linq

dynamic-linq