连接两个对象列表：一个列表中的所有属性，另一个列表中的某些属性

Question

I have two classes:

class Class1
{
    public int ProductId  { get; set; }
    public string ProductName  { get; set; }
    public int Amount  { get; set; }
    public string Category { get; set; }
}

class Class2
{
    public id ProductId  { get; set; }
    public DateTime UpdateTime { get; set; }
    public int ItemState  { get; set; }
    public decimal Price { get; set; }
    public string ImageUrl { get; set; }
}

I create two lists for each of this class:

public List<Class1> listClass1 { get; set; } = new List<Class1>();
public List<Class2> listClass2 { get; set; } = new List<Class2>();

Now I want to create a new list by joining both lists on the ProductID containing all properties from Class1 and just UpdateTime and ItemState from Class2 . What is the best way to do this?

(The ultimate goal is to let the user save the current session to let him continue with his work later, for this I need the complete listClass1 and the mentioned properties of listClass2 . The idea is to use an XmlSerializer on the merged list and save it into an XML file. To open the file, I want to deserialize it. If you have a better approach to let the user save his session, I'm all ears.)

Answer 1

I would suggest to make a third class which represents the joined parameter set.

public class Class1_2
{
    public int ProductId { get; set; }
    public string ProductName { get; set; }
    public int Amount { get; set; }
    public string Category { get; set; }

    public DateTime UpdateTime { get; set; }
    public int ItemState { get; set; }
}

How to join 2 Lists is described in LINQ Join 2 Lists . So you would end up with something like this:

List<Class1_2> joinedList = (from item1 in listClass1
                             join item2 in listClass2
                             on item1.ProductId equals item2.ProductId
                             select new Class1_2
                             {
                                 ProductId = item1.ProductId,
                                 Amount = item1.Amount,
                                 ProductName = item1.ProductName,
                                 Category = item1.Category,
                                 ItemState = item2.ItemState,
                                 UpdateTime = item2.UpdateTime
                             }).ToList();

Explanation: You join the items on the particular property. If it is equal in both lists you take the item and construct a new one with the selected properties. The join would also work without Class1_2 but then you get a result of dynamic type. The advantage of the new Class_1_2 is that you can use it for serialization with a defined structure.

EDIT

you could also use a second constructor in Class1_2

public Class1_2(Class1 c1, Class2 c2)
{
    ProductId = c1.ProductId;
    Amount = c1.Amount;
    ProductName = c1.ProductName;
    Category = c1.Category;
    ItemState = c2.ItemState;
    UpdateTime = c2.UpdateTime;
}

that would simplify a little the select statement to:

select new Class1_2(item1, item2)).ToList();