C# comparing 2 lists of objects while ignoring the key field

February 8, 2022

I am trying to compare 2 lists of objects for equality, but I want to ignore the key field.
How can I do this?

Here is an example:

public class myProduct
{
    int ID {get; set;}
    int field1 {get; set;}
    int field2 {get; set;}
}

<List>myProduct greenProducts = new <List>myProduct();
<List>myProduct purpleProducts = new <List>myProduct();

greenProducts.Add(new myProduct { ID = 1, field1 = 5, field2 = 8});
greenProducts.Add(new myProduct { ID = 2, field1 = 9, field2 = 12});
greenProducts.Add(new myProduct { ID = 3, field1 = 7, field2 = 7});

purpleProducts.Add(new myProduct { ID = 8, field1 = 5, field2 = 8});
purpleProducts.Add(new myProduct { ID = 9, field1 = 9, field2 = 12});
purpleProducts.Add(new myProduct { ID = 10, field1 = 7, field2 = 7});

If you ignore the key field (aka the ID field), these lists are exactly the same.

So I want my code to do something like this:

if (purpleProducts == greenProducts) //I WANT THE ID FIELD IGNORED FOR THE COMPARISON SO RESULT WITH ABOVE DATA WOULD BE TRUE
{
  //DO ACTION HERE
}

>Solution :

you can loop through it. Here is a loop that will make sure the number of duplicates are the same.

public class myProduct
{
    public int ID { get; set; }
    public int field1 { get; set; }
    public int field2 { get; set; }
}
List<myProduct> greenProducts = new List<myProduct>();
List<myProduct> purpleProducts = new List<myProduct>();

greenProducts.Add(new myProduct { ID = 1, field1 = 5, field2 = 8 });
greenProducts.Add(new myProduct { ID = 2, field1 = 9, field2 = 12 });
greenProducts.Add(new myProduct { ID = 3, field1 = 7, field2 = 7 });

purpleProducts.Add(new myProduct { ID = 8, field1 = 5, field2 = 8 });
purpleProducts.Add(new myProduct { ID = 9, field1 = 9, field2 = 12 });
purpleProducts.Add(new myProduct { ID = 10, field1 = 7, field2 = 7 });

var areEqual = true;
            
if (greenProducts.Count() != purpleProducts.Count()) areEqual = false;
if (areEqual)
{
    foreach (var item in greenProducts)
    {
        if(greenProducts.Where(g => g.field1 == item.field1 && g.field2 == item.field2).Count() != purpleProducts.Where(p => p.field1 == item.field1 && p.field2 == item.field2).Count())
        {
            areEqual = false;
            break;
        }
    }
}
if (areEqual)
{
    //DO ACTION HERE
}