Find all instances of Type in an object graph

Question

Lets say i have the following object graph

Parent : BaseEntity
  string1 SimpleString
  Middle Middle
  List Children (3)

Middle : BaseEntity
  string NormalStr
  int NiceInt
  RandomClass Ignore

 Child : BaseEntity
   string ChildString
   Parent Parent

In this example i want a way to give my Parent as input and get back a flat list {Parent, Middle, Child1, Child2, Child3}. It should work for any type of object graph.

Im trying to get there with reflection and recursion. The problem i run into is the cyclic reference between Parent and Child and i end up in an infinite loop.

How do i prevent this? I cant seem to get any "already seen" mechanism to work.

This is what i got so far. It works without the collection part, but that part is pretty important...

    public void TraverseThroughProperties(object myObject)
    {
        foreach (var prop in myObject.GetType().GetProperties())
        {
            var instance = prop.GetValue(myObject);
            if (instance is BaseEntity myBase)
                TraverseThroughProperties(instance);


            if (instance is ICollection collection)
            {
                foreach (var item in collection.OfType())
                    TraverseThroughProperties(item);
            }

            // Do something with myObject + prop
        }
    }

user_1612975 · Answer

If i understand the question correctly, I guess the easiest way would be keep a HashSet of the types you have visited.

public static void TraverseThroughProperties(object myObject, HashSet hashset = null)
{
   hashset ??= new HashSet();
   if (hashset.Contains(myObject.GetType()))
      return;
   hashset.Add(myObject.GetType());
   ...

Note : this might not be optimal as it will reject the same types. The other way is to keep a tuple of the parent child types visited. however once again this might filter more than expected.

public static void TraverseThroughProperties(object myObject, object parent, HashSet<(Type,Type)> hashset = null)
{
   hashset ??= new HashSet<(Type,Type)>();
   ...

Another way, is to hash the actual reference. Which would keep track of references, or once again, keep track of parent child references

public static void TraverseThroughProperties(object myObject, HashSet

Find all instances of Type in an object graph

1 Answers