Rule Definition
Whenever you work with objects in detached state, and especially if you test them for equality (usually in hash-based collections), you need to supply your own implementation of the equals() and hashCode() methods for your persistent classes. Nevertheless, it's possible to build a complex application with identity (default) equals as long as you exercise discipline when dealing with detached objects from different sessions. If this concept of equality isn't what you want, you must override equals() in your persistent classes.

Remediation
Check if you have instances from multiple sessions and implement Object.GetHashCode and Object.Equals if it is the case. If it is not the case, we recommend implementing it anyway to avoid issues during future evolutions.

Violation Code Sample

[Serializable]
public class MyObject
{
    public int n1 = 0;
    public int n2 = 0;
    public String str = null;
}

Fixed Code Sample

[Serializable]
public class MyObject
{
    public int n1 = 0;
    public int n2 = 0;
    public String str = null;

    public override int GetHashCode()
    {
        return n1;
    }

    public override bool Equals(Object obj)
    {
        if (obj == null || !(obj is MyObject))
            return false;
        else
            return n1 == ((MyObject)obj).n1;
    }

}