how to do inner join,left outerjoin between collections in C#

Question

Hi Friends,

I have two collection with more number of items like a million. I want to compare them to find out the below in C#

//how to find the matching items between Orders1 and Orders2
//how to find the Orders1 which are in Orders2
//how to find the Orders2 which are in Orders1
//how to find the Orders1 which are not in Orders2
//how to find the Orders2 which are not in Orders1

public class Order  
    {  
        public int OrderID { get; set; }         
        public string OrderDate { get; set; }  
        public string StoreID { get; set; }  
        public float TotalPrice { get; set; }  
  
    }  

static void Main(string[] args)
{
List<Order> Orders1 = new List<Order>();
Orders1.Add(new Order { OrderID = 1, StoreID = "A01", TotalPrice = 12.1F });
Orders1.Add(new Order { OrderID = 2, StoreID = "A02", TotalPrice = 12.2F });
Orders1.Add(new Order { OrderID = 3, StoreID = "A03", TotalPrice = 12.3F });
Orders1.Add(new Order { OrderID = 4, StoreID = "A04", TotalPrice = 12.4F });
Orders1.Add(new Order { OrderID = 1, StoreID = "A01", TotalPrice = 12.1F });
Orders1.Add(new Order { OrderID = 5, StoreID = "A05", TotalPrice = 12.5F });

        List<Order> Orders2 = new List<Order>();  
        Orders2.Add(new Order { OrderID = 1, StoreID = "A01", TotalPrice = 12.1F });  
        Orders2.Add(new Order { OrderID = 2, StoreID = "A02", TotalPrice = 12.2F });  
        Orders2.Add(new Order { OrderID = 2, StoreID = "A03", TotalPrice = 12.2F });  
        Orders2.Add(new Order { OrderID = 1, StoreID = "A01", TotalPrice = 12.1F });  
        Orders2.Add(new Order { OrderID = 5, StoreID = "A05", TotalPrice = 12.5F });  
        Orders2.Add(new Order { OrderID = 6, StoreID = "A06", TotalPrice = 12.6F });  
        Orders2.Add(new Order { OrderID = 7, StoreID = "A07", TotalPrice = 12.7F });  

        //how to find the matching items between Orders1 and Orders2  
        //how to find the Orders1 which are in Orders2  
        //how to find the Orders2 which are in Orders1  
        //how to find the Orders1 which are not in Orders2  
        //how to find the Orders2 which are not in Orders1  
    }  

Answer 1

See MSDN docs :

Perform inner joins
Perform left outer joins

Answer 2

@Code Heaven , Welcome to Microsoft Q&A, you could try the following code to get what you wanted.

I think the three previous questions are actually one question, and they all return common items to both Orders1 and Orders2.

Also, we need to Implement the interface IEqualityComparer to use Except and Intersect method to compare list of objects.

  public class OrderComparer : IEqualityComparer<Order>  
    {  
  
        public bool Equals(Order x, Order y)  
        {  
            if(x.OrderID==y.OrderID&&x.OrderDate==y.OrderDate&&x.TotalPrice==y.TotalPrice&&x.StoreID==y.StoreID)  
            {  
                return true;  
            }  
            else  
            {  
                return false;  
            }  
             
        }  
  
         
        public int GetHashCode(Order obj)  
        {  
            return 1;  
        }  
    }  

How to use it:

            OrderComparer comparer = new OrderComparer();  
            var result = Orders1.Intersect(Orders2, comparer);   //->how to find the matching items between Orders1 and Orders2 how to find the Orders1 which are in Orders2 how to find the Orders2 which are in Orders1  
            var d1 = Orders1.Except(Orders2, comparer); //how to find the Orders1 which are not in Orders2  
            var d2 = Orders2.Except(Orders1,comparer); //how to find the Orders2 which are not in Orders1  

Hope my code could help you.

Best Regards,
Jack

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