C# Compare two list of same object type

Question

I am trying to compare two list of same type using multiple properties of that type.

For example,

I have a class named Details

public class Details
{
    public   int id;
    public string symbol;
    public string code;
}

I have below two lists:

List<Details> list1 = new List<Details>();  
List<Details> list2 = new List<Details>();

list1.Add(new Details() { id=1,symbol="ANSI",code="NITE"});
list1.Add(new Details() { id = 1, symbol = "ANSI", code = "CALGO" });
list1.Add(new Details() { id = 1, symbol = "ANSI", code = "CANT" });
list1.Add(new Details() { id=2,symbol="ANSI",code="NITE"});
list1.Add(new Details() { id = 2, symbol = "ANSI", code = "CALGO" });
list1.Add(new Details() { id = 2, symbol = "ANSI", code = "CANT" });

list2.Add(new Details() { id = 1, symbol = "ANSI", code = "NITE" });
list2.Add(new Details() { id = 1, symbol = "ANSI", code = "CALGO" });
list2.Add(new Details() { id = 2, symbol = "ANSI", code = "NITE" });

I want only that data from List1 which has same id, symbol but different code.

So, in above scenario result will be as below.

list1.Add(new Details() { id = 1, symbol = "ANSI", code = "CANT" });
list1.Add(new Details() { id = 2, symbol = "ANSI", code = "CALGO" });
list1.Add(new Details() { id = 2, symbol = "ANSI", code = "CANT" });

It would be great if this can be achieved through Linq instead of using foreach.

I tried below but that's not correct.

var temp =list1.Where(x=>list2.Any(z=>x.id==z.id && string.Equals(x.symbol,z.symbol) && !string.Equals(x.code,z.code)));

Answer 1

It looks like you need rows to satisfy two conditions, not one, in order to make the output:

• There needs to be a match on id and symbol, and
• There must be no match on id, symbol, and code.

Here is how to do that with LINQ directly:

var tmp = list1.Where(x=>
    list2.Any(z=>x.id==z.id && x.symbol==z.symbol)
&& !list2.Any(z => x.id==z.id && x.symbol==z.symbol && x.code==z.code));

Demo.

An alternative based on applying De Morgan's laws:

var tmp = list1.Where(x=>
    list2.Any(z=>x.id==z.id && x.symbol==z.symbol)
 && list2.All(z => x.id!=z.id || x.symbol!=z.symbol || x.code!=z.code));

Demo.