比较 C# 中的两个对象列表 a 并检索具有不匹配记录的另一个列表

Question

我有两个对象列表，我需要比较这两个列表并获得不匹配记录的结果。

var oldlist = new List<Employee>{
new Employee(){EmployeeID=123,Name="XXXX",Gender="Male",code="CSE"},
new Employee(){EmployeeID=231,Name="FFF",Gender="Male",code="EC"},
new Employee(){EmployeeID=431,Name="GGG",Gender="Female",code="IT"},
new Employee(){EmployeeID=543,Name="DDD",Gender="Female",code="IT"}
}
var newlist = new List<Employee>{
new Employee(){EmployeeID=123,Name="HHH",Gender="Male",code="IT"},
new Employee(){EmployeeID=231,Name="JJJ",Gender="FeMale",code="CSE"},
new Employee(){EmployeeID=431,Name="GGG",Gender="Female",code="IT"},
new Employee(){EmployeeID=543,Name="DDD",Gender="Female",code="IT"}
}

在上面的代码中，EmployeeId 将是相同的，但任何其他值都会发生变化，例如 对于 EmployeeId 123 和 231 其他值（姓名、性别、代码）可以更改我只需要从上面的示例结果中的新列表中获取更改的记录应该只给出 employeeId 123 和 231 的记录，因为其余记录未更改。

Answer 1

您可以使用list1.except(list2) 找到两个列表之间的集合差异：-find-the-set-difference-between-two-lists-linq

 var result= oldlist.Except(newlist).ToList();

编辑：

您可以使用以下方法比较两个对象列表：

        List<Employee> list=new List<Employee>();
        foreach (var item in oldlist)
        {
            if(!newlist.Any(p=>p.EmployeeID==item.EmployeeID && p.Name == item.Name && p.Gender == item.Gender && p.code == item.code))
               list.Add(item);
        }

Answer 2

@HosseinSabziani 的回答也是正确的

或者，您可以使用 System.Linq.Enumerable 扩展来执行此操作，

像这样

员工类

   class Employee: IEqualityComparer<Employee>
   {
        public int EmployeeID { get; set; }
        public string Name { get; set; }
        public string Gender { get; set; }
        public string code { get; set; }
        public bool Equals(Employee x, Employee y)
        {
            return x.EmployeeID == y.EmployeeID;
        }
    
        public int GetHashCode(Employee obj)
        {
            return obj.EmployeeID.GetHashCode();
        }
   }

var unmatched = oldlist
.Where(old => !newlist.Any(newitem => new Employee().Equals(old, newitem)))
.ToList();

// or

var unmatched = oldlist
.Where(old => !newlist.Any(newitem => newitem.EmployeeID == old.EmployeeID))
.ToList();

还有 Join 和 Where 扩展名

var unmatched = (from old in oldlist
       join newitem in newlist on 
       old.EmployeeID equals 
       newitem.EmployeeID into joined from j in joined.DefaultIfEmpty()
       here j == null
       select old).ToList();

完整源代码

// Online C# Editor for free
// Write, Edit and Run your C# code using C# Online Compiler

using System;
using System.Collections.Generic;
using System.Linq;

public class HelloWorld
{
    class Employee: IEqualityComparer<Employee>
   {
        public int EmployeeID { get; set; }
        public string Name { get; set; }
        public string Gender { get; set; }
        public string code { get; set; }
        public bool Equals(Employee x, Employee y)
        {
            return x.EmployeeID == y.EmployeeID;
        }
    
        public int GetHashCode(Employee obj)
        {
            return obj.EmployeeID.GetHashCode();
        }
   }

    public static void Main(string[] args)
    {
        var oldlist = new List<Employee>{
           new Employee(){EmployeeID=123,Name="XXXX",Gender="Male",code="CSE"},
           new Employee(){EmployeeID=231,Name="FFF",Gender="Male",code="EC"},
           new Employee(){EmployeeID=431,Name="GGG",Gender="Female",code="IT"},
           new Employee(){EmployeeID=543,Name="DDD",Gender="Female",code="IT"}
       };
       
       var newlist = new List<Employee>{
          new Employee(){EmployeeID=123,Name="HHH",Gender="Male",code="IT"},
          new Employee(){EmployeeID=231,Name="JJJ",Gender="FeMale",code="CSE"},
          new Employee(){EmployeeID=431,Name="GGG",Gender="Female",code="IT"},
          new Employee(){EmployeeID=543,Name="DDD",Gender="Female",code="IT"}
       };
       
       var unmatched = oldlist.Where(old => !newlist.Any(newitem => new Employee().Equals(old, newitem))).ToList();
       
       Console.WriteLine ("Len: " + unmatched.Count);
    }
}