根据 C# 中的某些条件管理列表中的项目

Question

I have a couple of lists List<OldData> oldItems = new List<OldData>(); and List<NewData> newItems = new List<NewData>();

What I am trying to achieve here is to avoid the possibility of some redundant data coming in hence to check with some conditions before values are added into the list.

First up in the oldItems I will have some values stored and in the newItems list I will have a completely different set of values stored but it could always be the case that the newItems list may have some values that are already existing in the oldItems list.

The two variables that are in use are a Name variable and a path variable which stores a certain path

So First I want to check if there are any values where the name in the old items List is equal to the name in the new Items List , if There is an Item I want to check if the respective Path variable of the corresponding items are same ,

if it is same I can simply keep that item the way it is in the OldItems list , if that happens to be different I will Remove that from the old Items List (and later use the item in the new Item List)

So all the above in a nut shell ,

I want to check for in the Old Items List where there is a Name Corresponding to it in the new Item List If there is , I want to check if the corresponding values in the Path variable for the two items with the same name from the two List are the same or different

I have made a simple dummy application to demo this but really stuck on how i can implement the logic

any suggestion ?

class Program
{
    static void Main(string[] args)
    {

        List<OldData> oldItems = new List<OldData>();

        OldData oldData1 = new OldData();
        oldData1.Name = "Test01";
        oldData1.OriginalPath = "D:/Temp01";

        oldItems.Add(oldData1);


        OldData oldData2 = new OldData();
        oldData1.Name = "Test02";
        oldData1.OriginalPath = "D:/Temp02";
        oldItems.Add(oldData2);


        List<NewData> newItems = new List<NewData>();

        NewData newData1 = new NewData();
        newData1.Name = "Test01";
        newData1.OriginalPath = "D:/Temp01";

        newItems.Add(newData1);

        NewData newData2 = new NewData();
        oldData1.Name = "Test05";
        oldData1.OriginalPath = "D:/Temp05";
        newItems.Add(newData2);

        foreach (var item in oldItems)
        {
            //Check if there are any Names which are same from the new Item list
            //If if there is such an item check if the OriginalPath variable is the same iin both
            //If yes => Remove that particular item from the Old data List 
            //If Not => Keep that Item in  the old data List
        }
    }
}

class OldData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
}

class NewData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
}

In this case since the value Test01 is common to both List It will check if the path variable values corresponding to both items are the same or not

Answer 1

Your dummy application is using the same object (oldData1).

Please refer to the below code using simple LINQ.

class Program
{
    static void Main(string[] args)
    {
        List<OldData> oldItems = new List<OldData>();

        OldData oldData1 = new OldData();
        oldData1.Name = "Test01";
        oldData1.OriginalPath = "D:/Temp01";

        oldItems.Add(oldData1);


        OldData oldData2 = new OldData();
        oldData2.Name = "Test02";
        oldData2.OriginalPath = "D:/Temp02";
        oldItems.Add(oldData2);


        List<NewData> newItems = new List<NewData>();

        NewData newData1 = new NewData();
        newData1.Name = "Test01";
        newData1.OriginalPath = "D:/Temp01";

        newItems.Add(newData1);

        NewData newData2 = new NewData();
        newData2.Name = "Test05";
        newData2.OriginalPath = "D:/Temp05";
        newItems.Add(newData2);


        oldItems = oldItems.Where(x => newItems != null && !newItems.Any(y => x.Name == y.Name && x.OriginalPath == y.OriginalPath)).ToList();

    }
}

class OldData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
}

class NewData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
}

Answer 2

1) I would implement an interface with the shared properties

2) We make both the classes implement it (which is already done anyway)

3) We implement an EqualityComparer for the specific interface which will check only the properties we want from both the objects implementing our interface

That's an implementation example:

class Program
{
    static void Main(string[] args)
    {
        OldData oldData = new OldData
        {
            Name = "Pizza",
            OriginalPath = "Pozza"
        };

        NewData newData = new NewData
        {
            Name = "Pizza",
            OriginalPath = "Pozza"
        };

        var comparer = new CommonDataComparer();

        bool areEqual = comparer.Equals(oldData, newData);

        Console.WriteLine(areEqual);
    }
}

public interface ICommonData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
}

public class OldData : ICommonData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
    //Old other properties
}

public class NewData : ICommonData
{
    public string Name { get; set; }
    public string OriginalPath { get; set; }
    //New other properties
}

public class CommonDataComparer : IEqualityComparer<ICommonData>
{
    public bool Equals([AllowNull] ICommonData x, [AllowNull] ICommonData y)
    {
        return ((x?.Name == y?.Name) && (x?.OriginalPath == y?.OriginalPath));
    }

    public int GetHashCode([DisallowNull] ICommonData obj)
    {
        return obj.Name.GetHashCode() + obj.OriginalPath.GetHashCode();
    }
}

Output:

True

Answer 3

You're comparing strings so the == operator will work fine.

Here's a simple answer without using LINQ. Just a foreach loop with 2 conditions:

    for (int i = oldItems.Count - 1; i >= 0; i--)
    {
        OldData currentOldItem = oldItems[i] as OldData;
        foreach (var newItem in newItems) {
            if (currentOldItem.Name == newItem.Name) {
                if (currentOldItem.OriginalPath == newItem.OriginalPath) {
                    oldItems.RemoveAt(i);
                } 
            }
        }
    }