c# - 如何使用 linq 和 lambda 表达式从两个单独的列表中创建字典

Question

我正在练习 Linq 和 Lambda 表达式。我有两个这样的类:

public class Invoice
{
    public int InvoiceId { get; set; }
    public int EmployeeId { get; set; }
    public DateTime InvoiceDate { get; set; }
    public DateTime DueDate { get; set; }
    public bool? IsPaid { get; set; }
    public Invoice()
    {

    }
    public Invoice(int invoiceId, int employeeId, DateTime invoiceDate, DateTime dueDate, bool? isPaid)
    {
        InvoiceId = invoiceId;
        EmployeeId = employeeId;
        InvoiceDate = invoiceDate;
        DueDate = dueDate;
        IsPaid = isPaid;
    }
}

和:

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int ID { get; set; }
    public DateTime BirthDate { get; set; }
    public string Department { get; set; }
    public double Rating { get; set; }
    public int EmployeeType { get; set; }
    public Person(string firstName, string lastName, int id, DateTime birthDate, string department, double rating, int employeeType)
    {
        FirstName = firstName;
        LastName = lastName;
        ID = id;
        BirthDate = birthDate;
        Department = department;
        Rating = rating;
        EmployeeType = employeeType;
    }
    public Person()
    {

    }
}

我有两个列表:

List<Person> employee = new List<Person> {//some instances of Person here}

和

List<Invoice> invoices = new List<Invoice> {//some instances of invoice here}

如您所见，Invoice 类中的EmployeeId 是指Person 的ID。我想像这样创建一个字典:

var myDictionary=new Dictionary<"employeeName", List<employeeInvoices> >

linq 和 lambda 表达式是否可行？提前致谢

Answer 1

是的，你可以:

    Dictionary<string, List<Invoice>> result = employee.ToDictionary(e => string.Format("{0} {1}", e.FirstName, e.LastName),
        e => invoices.Where(i => i.EmployeeId == e.ID).ToList());

完整代码如下:

        var employee = new List<Person>() {
            new Person("FN", "LN", 1, new DateTime(1900, 1, 1), "", 1.1, 1),
            new Person("FN1", "LN1", 2, new DateTime(1900, 1, 1), "", 1.1, 1)
        };

        var invoices = new List<Invoice>() {
            new Invoice(1, 1, DateTime.Now, DateTime.Now, false),
            new Invoice(2, 2, DateTime.Now, DateTime.Now, false),
            new Invoice(3, 1, DateTime.Now, DateTime.Now, false),
        };

        Dictionary<string, List<Invoice>> result =
            employee.ToDictionary(e => string.Format("{0} {1}", e.FirstName, e.LastName),
                e => invoices.Where(i => i.EmployeeId == e.ID).ToList());