How to find the smallest assignable type in two types (duplicate)? [duplicate]

Answer 1

I'll have a default implementation and some well-known classes and interface sorted by priority to have in mind. Here my implementation:

private static List CommonTypesPriorities = new List 
                                       {
                                           typeof(IEnumerable), 
                                           typeof(Array), 
                                           typeof(IClonable)
                                       };

public static Type FindAssignableWith(this Type type1, Type type2)
{
    if(type1 == type2) 
        return type1;

    var baseClass = type1.FindBaseClassWith(type2);

    //if the base class is not object/null and it is not in the list, then return it.
    if(baseClass != typeof(object) && baseClass != null && !CommonTypesPriorities.Contains(type))
        return baseClass;

    var @interface = type1.FindInterfaceWith(type2);

    if(@interface == null)
        return baseClase;

    //if there's no base class and the found interface is not in the list, return it
    if(baseClass != null && !CommonTypesPriorities.Contains(@interface)                         
        return @interface;

    //Now we have some class and interfaces from the list.

    Type type = null;
    int currentPriority;

    //if the base class is in the list, then use it as the first choice
    if(baseClass != null && CommonTypesPriorities.Contains(type))
    {
        type = baseClass;
        currentPriority = CommonTypesPriorities.IndexOf(type);
    }

    var interfaces1 = type1.GetInterfaces();
    var interfaces2 = type2.GetInterfaces();

    foreach(var i in interfaces1)
    {
        if(interfaces2.Contains(i))
        {
            //We found a common interface. Let's check if it has more priority than the current one
            var priority = CommonTypesPriorities.IndexOf(i);
            if(i >= 0 && i < currentPriority)
            {
                currentPriority = priority;
                type = i;
            }
        }
    }

    return type;

}

Hope it helps.