/// <summary>
/// Creates a deep copy of an object using the supplied dictionary of visited objects as
/// a source of objects already encountered in the copy traversal. The dictionary of visited
/// objects is used for holding objects that have already been copied, to avoid erroneous
/// duplication of parts of the object graph.
/// </summary>
/// <param name="instance">The object to be copied.</param>
/// <param name="visited">The graph of objects visited so far.</param>
/// <returns></returns>
private static object Clone(this object instance, VisitedGraph visited)
{
if (instance == null)
{
return(null);
}
Type instanceType = instance.GetType();
if (instanceType.IsValueType || instanceType == typeof(string))
{
return(instance); // Value types and strings are immutable
}
else if (instanceType.IsArray)
{
int length = ((Array)instance).Length;
Array copied = (Array)Activator.CreateInstance(instanceType, length);
visited.Add(instance, copied);
for (int i = 0; i < length; ++i)
{
copied.SetValue(((Array)instance).GetValue(i).Clone(visited), i);
}
return(copied);
}
else
{
return(Clone(instance, visited, InstanceCreator.GetInstance(instanceType)));
}
}
private static object Clone(this object instance, VisitedGraph visited, object copy)
{
visited.Add(instance, copy);
var type = instance.GetType();
foreach (var field in GetTypeCopyableFieldList(type))
{
object value = field.Getter(instance);
object cloned;
if (value == null)
{
cloned = null;
}
else if (!visited.TryGetValue(value, out cloned))
{
cloned = value.Clone(visited);
}
field.Setter(copy, cloned);
}
return(copy);
}
