Compare two list of objects a in C# and retrieve another list with un match records-CodePudding

I've two list of object I need to compare this two lists and get result with unmatched records.

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"}
}

In above code EmployeeId will be same but there will be change in any other values like for EmployeeId 123 and 231 other values(Name,Gender,code)can changed I need to get only the changed records from newlist in above example result should give only records with employeeId 123 and 231 because remaining records are unchanged.

CodePudding user response：

you can use list1.except(list2) to find the set difference between two lists: -find-the-set-difference-between-two-lists-linq

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

edit:

You can use the following method to compare two lists of objects:

        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);
        }

CodePudding user response：

@HosseinSabziani answer is also correct

Alternatively, You can use System.Linq.Enumerable extensions to do this,

Like this

Employee class

   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();

Also with Join and Where extension

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();

full source code

// 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);
    }
}