Save file - xmlSerializer

Your error is in new XmlSerializer(typeof(type));. You don't need typeof. new XmlSerializer(type); is enough.

Since you serialize file object (and its type can be determined in the function) you don't have to pass its type. So your code can be re-written as

public void Save<T>(T file, String path)
{
    XmlSerializer serializer = new XmlSerializer(typeof(T));

    using (StreamWriter writer = new StreamWriter(path))
    {
        serializer.Serialize(writer, file);
    }
}