Type casting object[] to generic type K which is also an array

I try to write a generic type casting method which will work for both complex objects and arrays of objects. Below is my code:

public void Test()
{
     MyClass2[] t2 = m.MapItem<MyClass1[], MyClass2[]>(t1);
     return;
}

public K MapItem<T, K>(T source)
{
    if (typeof(T).IsArray && typeof(K).IsArray)
    {
        Type ek = typeof(K).GetElementType();
        IList sourceList = (IList)source;
        List<object> tmp = new List<object>();
        for (int i = 0; i < sourceList.Count; i++)
        {
            var k = Activator.CreateInstance(ek);
            tmp.Add(k);
        }
        var resultObj = tmp.ToArray();
        MapItem(source, resultObj);

        //Here i have resultObj is an object[] of the results,
        //which is to be casted result type K
        //BUT DOES NOT WORK!!!
        return (K)Convert.ChangeType(resultObj, typeof(K));

    }
    else
    {
        MethodInfo myMapperMethod = GetMyMapperMethodForThisType(typeof(T), typeof(K));
        return (K)myMapperMethod.Invoke(null, new object[] { source });
    }
}

public K MapItem<T, K>(T source, K dest)
{
    if (typeof(T).IsArray && typeof(K).IsArray)
    {
        IList sourceList = (IList)source;
        IList destList = (IList)dest;
        for (int i = 0; i < sourceList.Count; i++)
        {
            MapItem(sourceList[i], destList[i]);
        }
        return dest;
    }
    else
    {
        MethodInfo myMapperMethod = GetMyMapperMethodForThisType(typeof(T),typeof(K));
        return (K) myMapperMethod.Invoke(null, new object[] { source, dest });
    }
}

private MethodInfo GetMyMapperMethodForThisType(Type type1, Type type2)
{
    //some code to find appropriate function...
}

But, return (K) Convert.ChangeType(y, typeof(K)); cannot cast from object[] to K. How can I do this casting to return K from object[]?

Note: json serialization works but I don't want to use reflection or serialization.

  string jsonStr = JsonConvert.SerializeObject(resultObj);
  return JsonConvert.DeserializeObject<K>(jsonStr);