differences between two objects in C#

Question

I was wondering how I would find the difference between two objects of the same class. So if I had a Person class with the only difference being Age it will return the field

Answer 1

Here's some simple code I use for just such a thing while debugging:

    //This structure represents the comparison of one member of an object to the corresponding member of another object.
    public struct MemberComparison
    {
        public readonly MemberInfo Member; //Which member this Comparison compares
        public readonly object Value1, Value2;//The values of each object's respective member
        public MemberComparison(MemberInfo member, object value1, object value2)
        {
            Member = member;
            Value1 = value1;
            Value2 = value2;
        }

        public override string ToString()
        {
            return Member.Name + ": " + Value1.ToString() + (Value1.Equals(Value2) ? " == " : " != ") + Value2.ToString();
        }
    }

    //This method can be used to get a list of MemberComparison values that represent the fields and/or properties that differ between the two objects.
    public List ReflectiveCompare(T x, T y)
    {
        List list = new List();//The list to be returned

        foreach (MemberInfo m in typeof(T).GetMembers(BindingFlags.NonPublic | BindingFlags.Instance))
            //Only look at fields and properties.
            //This could be changed to include methods, but you'd have to get values to pass to the methods you want to compare
            if (m.MemberType == MemberTypes.Field)
            {
                FieldInfo field = (FieldInfo)m;
                var xValue = field.GetValue(x);
                var yValue = field.GetValue(y);
                if (!object.Equals(xValue, yValue))//Add a new comparison to the list if the value of the member defined on 'x' isn't equal to the value of the member defined on 'y'.
                    list.Add(new MemberComparison(field, yValue, xValue));
            }
            else if (m.MemberType == MemberTypes.Property)
            {
                var prop = (PropertyInfo)m;
                if (prop.CanRead && prop.GetGetMethod().GetParameters().Length == 0)
                {
                    var xValue = prop.GetValue(x, null);
                    var yValue = prop.GetValue(y, null);
                    if (!object.Equals(xValue, yValue))
                        list.Add(new MemberComparison(prop, xValue, yValue));
                }
                else//Ignore properties that aren't readable or are indexers
                    continue;
            }
        return list;
    }

To use it, your code might look something like this:

public static void Main()
{
    MyObject object1 = new MyObject();
    MyObject object2 = new MyObject();
    // ...Code that changes object1 and/or object2...

    //Here's your answer: a list of what's different between the 2 objects, and each of their different values.
    //No type parameters are needed here- typeof(MyObject) is implied by the coincident types of both parameters.
    List changes = ReflectiveCompare(object1, object2);
}