What is the best way to compare two entity framework entities?

Question

Hi All,

I want to know the most efficient way of comparing two entities of the same type.

One entity is created from an xml file by hand ( ie new instance and manually set properties) and the other is retvied from my object context.

I want to know if the property values are the same in each instance.

My first thoughts are to generate a hash of the property values from each object and compare the hashes, but there might be another way, or a built in way?

Any suggestions would be welcome.

Many thanks,

James

UPDATE

I came up with this:

static class ObjectComparator<T>
{
    static bool CompareProperties(T newObject, T oldObject)
    {
        if (newObject.GetType().GetProperties().Length != oldObject.GetType().GetProperties().Length)
        {
            return false;
        }
        else
        {
            var oldProperties = oldObject.GetType().GetProperties();

            foreach (PropertyInfo newProperty in newObject.GetType().GetProperties())
            {
                try
                {
                    PropertyInfo oldProperty = oldProperties.Single<PropertyInfo>(pi => pi.Name == newProperty.Name);

                    if (newProperty.GetValue(newObject, null) != oldProperty.GetValue(oldObject, null))
                    {
                        return false;
                    }
                }
                catch
                {
                    return false;
                }
            }

            return true;
        }
    }
}

I haven't tested it yet, it is more of a food for thought to generate some more ideas from the group.

One thing that might be a problem is comparing properties that have entity values themselves, if the default comparator compares on object reference then it will never be true. A possible fix is to overload the equality operator on my entities so that it compares on entity ID.

Answer 1

Override the Equals method of your object and write an implementation that compares the properties that make it equal.

    public override bool Equals(object obj)
    {
        return MyProperty == ((MyObject)obj).MyProperty
    }