Question

我会尽力解释我遇到的情况。基本上我有两个清单。

现在我要做的是选择其他列表中不存在的所有值。但问题是，如果我使用$searchpath = "e:\" # Find a unique list of directories that contains a revit backup file (*.*.rvt) $a = Get-ChildItem -Path $searchpath -Include *.*.rvt -Recurse | Select Directory | Get-Unique -AsString # For each folder that contains a single revit backup file (*.*.rvt)... # - Sort by modified time # - Select all except first 5 $a | foreach { $b += Get-ChildItem -Path $_.Directory.FullName -Include *.*.rvt | Sort-Object LastWriteTime -descending | select-object -skip 5 -property Directory,Name,CreationTime,LastWriteTime } $b | Out-GridView -Title "Old Backups" -PassThru扩展方法并选择两个属性，则它总是返回0值。

这是我的代码：

第一个列表：

All

第二个清单：

IList<Person> lstOne = new List<Person>();
        lstOne.Add(new Person()
            {
                ID = 1, 
                IDSecond = 2,
                IDThird = 2
            });
        lstOne.Add(new Person()
            {
                ID = 2, 
                IDSecond = 3,
                IDThird = 2
            });

现在，如果我想选择第一个列表中不存在的第二个列表，我通常会这样做：

        IList<Person> lstFinal = new List<Person>();
        lstFinal.Add(new Person()
        {
            ID = 1,
            IDSecond = 2,
            IDThird = 2
        });
        lstFinal.Add(new Person()
        {
            ID = 3,
            IDSecond = 4,
            IDThird = 2
        });
        lstFinal.Add(new Person()
        {
            ID = 4,
            IDSecond = 5,
            IDThird = 2
        });

这很好用，结果将是两个值：

var resultOne = lstFinal.Where(c => lstOne
.All(x => x.ID != c.ID && x.IDSecond != c.IDSecond)).ToList();

如果我选择一个或两个属性，它可以正常工作。但是如果我在项目中添加了我需要的其他属性，结果总是为零：

ID: 3 and ID: 4

我的问题应该是这段代码：

var resultOne = lstFinal.Where(c => lstOne
.All(x => x.ID != c.ID && x.IDSecond != c.IDSecond && x.IDThird != c.IDThird)).ToList();

返回两个值而不是没有？我期待它返回它，但它返回0值：

var resultOne = lstFinal.Where(c => lstOne
.All(x => x.ID != c.ID && x.IDSecond != c.IDSecond && x.IDThird != c.IDThird)).ToList();

Answer 1

Enumerable已经定义了一些为您执行此操作的功能，因此您不必重新发明轮子

选中此MSDN

class Compare : IEqualityComparer<Person>
    {
        public bool Equals(Person x, Person y)
        {
            if (x == null || y == null)
            {
                return false;
            }
            return x.ID == y.ID && x.IDSecond == y.IDSecond;
        }

        public int GetHashCode(Person obj)
        {
            return 1;
        }
    }

    class FullCompare : IEqualityComparer<Person>
    {
        public bool Equals(Person x, Person y)
        {
            if (x == null || y == null)
            {
                return false;
            }
            return x.ID == y.ID && x.IDSecond == y.IDSecond && x.IDThird == y.IDThird;
        }

        public int GetHashCode(Person obj)
        {
            return 1;
        }
    }

    class Person
    {
        public int ID { get; set; }
        public int IDSecond { get; set; }
        public int IDThird { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {
            IList<Person> lstOne = new List<Person>();
            lstOne.Add(new Person()
            {
                ID = 1,
                IDSecond = 2,
                IDThird = 2
            });
            lstOne.Add(new Person()
            {
                ID = 2,
                IDSecond = 3,
                IDThird = 2
            });

            IList<Person> lstFinal = new List<Person>();
            lstFinal.Add(new Person()
            {
                ID = 1,
                IDSecond = 2,
                IDThird = 2
            });
            lstFinal.Add(new Person()
            {
                ID = 3,
                IDSecond = 4,
                IDThird = 2
            });
            lstFinal.Add(new Person()
            {
                ID = 4,
                IDSecond = 5,
                IDThird = 2
            });


            var a = lstFinal.Except(lstOne, new Compare());
            var b = lstFinal.Except(lstOne, new FullCompare());
            a.ToList().ForEach(s => Console.WriteLine(s.ID));
            b.ToList().ForEach(s => Console.WriteLine(s.ID));

            Console.ReadLine();
            //Console.WriteLine();
        }
    }

所有扩展方法都不返回具有两个以上属性的预期值

1 个答案: