Question

I want to do a breadth first search of a tree using a Queue

var q = new Queue<T>();  q.Enqueue(Root);  foreach(T root in q) {   foreach(T t in root.Children)     q.Enqueue(t); } 

However I get a ‘Collection was modified after the enumerator was instantiated.’ Exception.

Is there a C# type that I can do this with?

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Edit: a little reading make me thing I might be doing this totally wrong.

Is there a way to use a foreach to dequeue from a Queue?

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this works but is ugly (OMHO)

var q = new Queue<T>();  q.Enqueue(Root);  while(q.Count > 0) {   T root = q.Dequeue();   foreach(T t in root.Children)     q.Enqueue(t); } 

Answer 1

You can’t enumerate over an IEnumerable and change the same IEnumerable at the same time. I don’t think there is a C# Collection that will allow this.