使用Linq更新嵌套列表值？

Question

I am trying to update a nested list in C# which looks like this

List <Users >
- UserType
- List <UserComponents >
- - UserComponentKey
- - Count

Here's a written example:
List of users: UserType = 1
UserComponents
- UserComponentKey = XYZ
- Count = 3

UserType = 2
UserComponents
- UserComponentKey = XYZ
- Count = 7

I need to update UserComponentKey XYZ for UserType 2 only, currently my updates are broken and updates XYZ for all user types. Here is my current methods which do not work as they update the UserComponent count value for ALL usertypes which contain the specified component key, and not the specific usertype I am targeting.

CLASSES:

public class Users
{
    public string UserType { get; set; }
    public List<UserComponent> UserComponents { get; set; }
}

public class UserComponent
{
    public string UserComponentKey { get; set; }
    public int Count { get; set; }
}

METHOD 1:

Users.Where(us => us.UserType == "2")
     .First().UserComponents
     .Where(uc => uc.UserComponentKey == "XYZ")
     .First().Count = value;

METHOD 2:

if(users.UserType == "2")
{
   foreach(var component in users.UserComponents)
   {
       switch(component.UserComponentKey)
       {
          case "XYZ":
          component.Count = value;
          break;
       }
    }
}

CODE GENERATING LIST (similar to): List UserComponents = new List();

if (Item.UserAddOn != null)
    {
        for (var i = 0; i < Item.UserAddOn.First().Count; i++)
        {
            UserComponents.Add(new UserComponent
            {
                UserComponentKey = Item.UserAddOn[i].ComponentKey,
                Count = 0
             });
         }
    }

if (Item.User != null)
    {
        for (var i = 0; i < Item.User.First().Count; i++)
        {
             Users.Add(new User()
             {
                 UserType = Item.User[i].ComponentKey,
                 Count = 0,
                 UsersComponents = UserComponents
             });
         }
     }

I have stripped out actual values etc, but hopefully someone can point me in the right direction here.

Thanks!

Answer 1

Your first call to First() is wrong. Try it like this:

Users.Where((us) => us.UserType == "2")
     .Select((us) => us.UserComponents)
     .Where((uc) => uc.UserComponentKey == "XYZ")
     .First()
     .Count = value;

Suggestion: Why don't you make UserType an int ?

Answer 2

May be it helps:

        List<Users> _users = new List<Users>();
        _users.Add(new Users() { UserType = "1", UserComponents = new List<UserComponent>() { new UserComponent() { Count = 0, UserComponentKey = "XYZ" } } });
        _users.Add(new Users() { UserType = "2", UserComponents = new List<UserComponent>() { new UserComponent() { Count = 2, UserComponentKey = "XYZ" } } });
        _users.Add(new Users() { UserType = "3", UserComponents = new List<UserComponent>() { new UserComponent() { Count = 5, UserComponentKey = "XYZ" } } });

        _users.Where(us => us.UserType == "2").First().UserComponents.Where(uc => uc.UserComponentKey == "XYZ").First().Count = 356;

        foreach (Users us in _users)
        {
            Console.WriteLine("UserType: " + us.UserType);
            foreach (UserComponent uc in us.UserComponents)
            {
                Console.WriteLine("Key: {0} Value: {1}", uc.UserComponentKey, uc.Count);
            }
        }

Answer 3

I'm missing information to write a snippet you can use so I will simply explain it. An object variable is in reality a reference (a pointer, if you are familiar with C++/C) to the location where the object reside. When you add an object to a list, you add it's location. If you add this object to multiple list, you give the same location and therefor, editing one of them will edit all of them.

var uc1 = new UserComponent { Count = 1 };
var uc2 = new UserComponent { Count = 2 };
var uc3 = new UserComponent { Count = 2 };

var u1 = new User();
var u2 = new User();

u1.UserComponents.Add(uc1);
u1.UserComponents.Add(uc2);

u2.UserComponents.Add(uc1);
u2.UserComponents.Add(uc3);

Console.Write(u1.UserComponents[0].Count); //Outputs 1
Console.Write(u1.UserComponents[1].Count); //Outputs 2
Console.Write(u2.UserComponents[0].Count); //Outputs 1
Console.Write(u2.UserComponents[1].Count); //Outputs 2

u2.UserComponents[0].Count = 5;
u2.UserComponents[1].Count = 6;

Console.Write(u1.UserComponents[0].Count); //Outputs 5
Console.Write(u1.UserComponents[1].Count); //Outputs 6
Console.Write(u2.UserComponents[0].Count); //Outputs 5
Console.Write(u2.UserComponents[1].Count); //Outputs 2

So your code to change values is fine, but when you build up your list, you need to create distinct UserComponents if they are not linked together.