c# compare the data in two object models

Question

I have a dialog, when spawned it gets populated with the data in an object model. At this point the data is copied and stored in a \"backup\" object model. When the user h

Answer 1

I understand your question to be how one can compare two objects for value equality (as opposed to reference equality) without prior knowledge of the types, such as if they implement IEquatable or override Equals.

To do this I recommend two options:

A. Use an all-purpose serialization class to serialize both objects and compare their value. For example I have a class called XmlSerializer that takes any object and serializes its public properties as an XML document. Two objects that have the same values and possibly the same reference will have the same values in this sense.

B. Using reflection, compare the values of all of the properties of both objects, like:

bool Equal(object a, object b)
{
    // They're both null.
    if (a == null && b == null) return true;
    // One is null, so they can't be the same.
    if (a == null || b == null) return false;
    // How can they be the same if they're different types?
    if (a.GetType() != b.GetType()) return false; 
    var Props = a.GetType().GetProperties();
    foreach(var Prop in Props)
    {
        // See notes *
        var aPropValue = Prop.GetValue(a) ?? string.Empty;
        var bPropValue = Prop.GetValue(b) ?? string.Empty;
        if(aPropValue.ToString() != bPropValue.ToString())
            return false;
    }
    return true;
}

Here we're assuming that we can easily compare the properties, like if they all implement IConvertible, or correctly override ToString. If that's not the case I would check if they implement IConvertible and if not, recursively call Equal() on the properties.

This only works if you're content with comparing public properties. Of course you COULD check private and protected fields and properties too, but if you know so little about the objects you're probably asking for trouble but doing so.