Find-or-insert with only one lookup in c# dictionary

Question

I\'m a former C++/STL programmer trying to code a fast marching algorithm using c#/.NET technology...

I\'m searching for an equivalent of STL method \"map::insert\"

Answer 1

Sadly, there isn't one in bcl's implementation. The closest alternative is doing two lookups, but one can have a generic extension method to make it easy, as shown here

public static T GetOrAdd(this IDictionary dict, S key, 
                               Func valueCreator)
{
    T value;
    return dict.TryGetValue(key, out value) ? value : dict[key] = valueCreator();
}

But there is C5's implementation which does this out of the box. The method definition looks like this:

public virtual bool FindOrAdd(K key, ref V value)
{

}

I don't know why they don't accept a Func instead of V to defer object creation. C5 has a lot of nice similar tricks, for eg,

public virtual bool Remove(K key, out V value)

public virtual bool Update(K key, V value, out V oldvalue)

public virtual bool UpdateOrAdd(K key, V value, out V oldvalue)