C# LINQ 如何将父列表和两个嵌套子列表展平为新列表

Question

我需要将一个父列表和两个子列表合并为一个列表。我如何使用 C# 和 linq 来做到这一点？

这是我的代码...

public class Customer
{
    public string FirstName { get; set;}
    public string LastName { get; set;}
    // need to flatten these lists
    public List<CreditCard> CreditCards { get; set;}
    public List<Address> Addresses{ get; set;}
}

//  Customer has CreditCards list and Addresses list
List<Customer> allCustomers = _db.GetAllCustomers();

// how to flatten Customer, CreditCards list, and Addresses list into one flattened record/list?

var result = allCustomers.GroupBy().SelectMany(); // how to flatten nested lists?

因此，结果列表将包含看起来扁平化的项目，如下所示：

Joe, Blow, Visa, Master Card, 38 Oak Street, 432 Main Avenue

Sally、Cupcake、Discover、万事达卡、29 Maple Grove、887 Nut Street

它将展平客户的名字、姓氏、信用卡列表和地址列表。

感谢您的任何反馈！

Answer 1

实施IEnumerable：

public class Customer : IEnumerable<string>
{
    public string FirstName {get; set;}
    public string LastName {get; set;}
    public List<CreditCard> CreditCards {get; set;}
    public List<Address> Addresses{get; set;}

    public IEnumerator<string> GetEnumerator()
    {
        yield return FirstName;
        yield return LastName;
        foreach (CreditCard c in CreditCards)
        {
            yield return c.ToString();
        }
        foreach (Address a in Addresses)
        {
            yield return a.ToString();
        }
    }
}

...

var result = allCustomers.SelectMany(c => c);

注意：这只是一个例子。