Checking sub-equality of two complex objects

There are several techniques, but here is something to start with. I have used an extension method which works all the way down to object (why not), but you could restrict it to higher levels of make it part of your base class itself.

Note that reflection is relatively expensive so if it is the sort of operation that you are doing often, you should consider caching the relevant PropertyInfos.

namespace ConsoleApp1 { using System; using System.Collections; using System.Collections.Generic; using System.Reflection; public class BaseClass<T> { public string prop1 { get; set; } public List<T> prop2 { get; set; } //B is a user-defined type } public class DescendentClass<T> : BaseClass<T> { } public static class DeepComparer { public static bool IsDeeplyEquivalent(this object current, object other) { if (current.Equals(other)) return true; Type currentType = current.GetType(); // Assumption, cannot be equivalent if another class (descendent classes??) if (currentType != other.GetType()) { return false; } foreach (PropertyInfo propertyInfo in currentType.GetProperties()) { object currentValue = propertyInfo.GetValue(current, null); object otherValue = propertyInfo.GetValue(other, null); // Assumption, nulls for a given property are considered equivalent if (currentValue == null && otherValue == null) { continue; } // One is null, the other isn't so are not equal if (currentValue == null || otherValue == null) { return false; } ICollection currentCollection = currentValue as ICollection; if (currentCollection == null) { // Not a collection, just check equality if (!currentValue.Equals(otherValue)) { return false; } } else { // Collection, not interested whether list/array/etc are same object, just that they contain equal elements // questioner guaranteed that all elements are unique HashSet<object> elements = new HashSet<object>(); foreach (object o in currentCollection) { elements.Add(o); } List<object> otherElements = new List<object>(); foreach (object o in (ICollection)otherValue) { otherElements.Add(o); } // cast below can be safely made because we have already asserted that // current and other are the same type if (!elements.SetEquals(otherElements)) { return false; } } } return true; } } public class Program { public static void Main(string[] args) { BaseClass<int> a1 = new BaseClass<int>{prop1 = "Foo", prop2 = new List<int>{1, 2, 3}}; BaseClass<int> a2 = new BaseClass<int>{prop1 = "Foo", prop2 = new List<int>{2, 1, 3}}; BaseClass<int> a3 = new BaseClass<int>{prop1 = "Bar", prop2 = new List<int>{2, 1, 3}}; BaseClass<string> a4 = new BaseClass<string>{prop1 = "Bar", prop2 = new List<string>()}; BaseClass<int> a5 = new BaseClass<int>{prop1 = "Bar", prop2 = new List<int>{1, 3}}; DateTime d1 = DateTime.Today; DateTime d2 = DateTime.Today; List<string> s1 = new List<string>{"s1", "s2"}; string[] s2 = {"s1", "s2"}; BaseClass<DayOfWeek> b1 = new BaseClass<DayOfWeek>{prop1 = "Bar", prop2 = new List<DayOfWeek>{DayOfWeek.Monday, DayOfWeek.Tuesday}}; DescendentClass<DayOfWeek> b2 = new DescendentClass<DayOfWeek>{prop1 = "Bar", prop2 = new List<DayOfWeek>{DayOfWeek.Monday, DayOfWeek.Tuesday}}; Console.WriteLine("a1 == a2 : " + a1.IsDeeplyEquivalent(a2)); // true, different order ignored Console.WriteLine("a1 == a3 : " + a1.IsDeeplyEquivalent(a3)); // false, different prop1 Console.WriteLine("a3 == a4 : " + a3.IsDeeplyEquivalent(a4)); // false, different types Console.WriteLine("a3 == a5 : " + a3.IsDeeplyEquivalent(a5)); // false, difference in list elements Console.WriteLine("d1 == d2 : " + d1.IsDeeplyEquivalent(d2)); // true Console.WriteLine("s1 == s2 : " + s1.IsDeeplyEquivalent(s2)); // false, different types Console.WriteLine("b1 == b2 : " + s1.IsDeeplyEquivalent(s2)); // false, different types Console.WriteLine("b1 == b1 : " + b1.IsDeeplyEquivalent(b1)); // true, same object Console.ReadLine(); } } }