从两个列表中过滤掉重复项，如果重复则更改对象属性值

Question

我有两个列表 AuthorList 和 AuthorList2。目前我正在使用带有简单 IEqualityComparer 类的联合。 我希望有一个没有来自 AuthorList 和 AuthorList2 的重复项的结果列表，如果这些列表中有任何重复项，则需要将它们从列表中删除，并且需要将重复项的 Author 类 Assigned 属性设置为 true。

来自两个 AuthorLists 的现有信息：

ProductID 和分配

• 1，假
• 2，错误
• 3，错误
• 1，假

结果列表：

ProductID 和分配

• 1，真
• 2，错误
• 3，错误

逻辑需要过滤掉重复项，如果这两个列表具有相同的元素，则更改 false -> true。

namespace HelloWorld
{
     class Hello
      {
        static void Main()
        {

            List<Author> AuthorList = new List<Author>
            {
                new Author(1, false),
                new Author(2, false),
                new Author(3, false)
            };


            List<Author> AuthorList2 = new List<Author>
            {
                new Author(1, false)
            };

            var compareById = new AuthorComparer(false);

            var result = AuthorList.Union(AuthorList2, compareById);

            foreach (var item in result)
            {
                Console.WriteLine("Result: {0},{1}", item.ProductId, item.Assigned);
            }

            Console.ReadKey();
        }

        public class AuthorComparer : IEqualityComparer<Author>
        {
            private bool m_withValue;

            public AuthorComparer(bool withValue)
            {
                m_withValue = withValue;
            }

            public bool Equals(Author x, Author y)
            {
                return (x.ProductId == y.ProductId);
            }

            public int GetHashCode(Author x)
            {
                return x.ProductId.GetHashCode();
            }
        }

        public class Author
        {
            private int productId;
            private bool assigned;

            public Author(int productId, bool assigned)
            {
                this.productId = productId;
                this.assigned = assigned;
            }

            public int ProductId
            {
                get { return productId; }
                set { productId = value; }
            }

            public bool Assigned
            {
                get { return assigned; }
                set { assigned = value; }
            }
        }
      }
    }

Answer 1

你要找的代码是这样的：

AuthorList.ForEach(a => a.Assigned = AuthorList2.Exists(b => b.ProductId == a.ProductId));

您根本不需要IEqualityComparer。

完整的工作代码：

namespace HelloWorld
{
    class Hello
    {
        static void Main()
        {

            List<Author> AuthorList = new List<Author>
            {
                new Author(1, false),
                new Author(2, false),
                new Author(3, false)
            };


            List<Author> AuthorList2 = new List<Author>
            {
                new Author(1, false)
            };

            AuthorList.ForEach(a => a.Assigned = AuthorList2.Exists(b => b.ProductId == a.ProductId));

            foreach (var item in AuthorList)
            {
                Console.WriteLine("Result: {0},{1}", item.ProductId, item.Assigned);
            }

            Console.ReadKey();
        }

        public class Author
        {
            public Author(int productId, bool assigned)
            {
                this.ProductId = productId;
                this.Assigned = assigned;
            }

            public int ProductId { get; set; }

            public bool Assigned { get; set; }
        }
    }
}

Answer 2

使用您的比较器，您可以使用：

foreach (var author in AuthorList.Intersect(AuthorList2, compareById))
{
    author.Assigned = true;
}

如果您不需要比较器来做其他事情，您也可以轻松做到这一点：

var author2Ids = new HashSet<int>(AuthorList2.Select(a => a.ProductId));
foreach (var author in AuthorList.Where(a => author2Ids.Contains(a.ProductId)))
{
    author.Assigned = true;
}

...但是如果您需要比较器来做其他事情，或者它可能变得更复杂，我会坚持使用它。

Answer 3

试试这样的东西。请仔细看!

       //Separate out different entries from both the lists
        var diffList = AuthorList.Where(x => !AuthorList2.Any(y => y.ProductId== x.ProductId && y.Assigned== x.Assigned)).ToList();
       //Separate out common entries from both the list
        var commonList = AuthorList.Where(x => AuthorList2.Any(y => y.ProductId== x.ProductId && y.Assigned== x.Assigned)).ToList();
        //Change value of Assigned
        commonList.ForEach(x => x.Assigned = !x.Assigned);
       //Merge both the lists
       diffList.AddRange(commonList);

POC：DotNetFiddler

Answer 4

这将产生一个新的元素列表而不改变源：

private static List<Author> FilterDuplicates(List<Author> x, List<Author> y)
{
     return x.Select(author => new Author(author.ProductId, y.Exists(a => a.ProductId == author.ProductId))).ToList();
}