Generic Key/Value pair collection in that preserves insertion order?

There is not. However, System.Collections.Specialized.OrderedDictionary should solve most need for it.

EDIT: Another option is to turn this into a Generic. I haven’t tested it but it compiles (C# 6) and should work. However, it will still have the same limitations that Ondrej Petrzilka mentions in comments below.

    public class OrderdDictionary<T, K>
    {
        public OrderedDictionary UnderlyingCollection { get; } = new OrderedDictionary();

        public K this[T key]
        {
            get
            {
                return (K)UnderlyingCollection[key];
            }
            set
            {
                UnderlyingCollection[key] = value;
            }
        }

        public K this[int index]
        {
            get
            {
                return (K)UnderlyingCollection[index];
            }
            set
            {
                UnderlyingCollection[index] = value;
            }
        }
        public ICollection<T> Keys => UnderlyingCollection.Keys.OfType<T>().ToList();
        public ICollection<K> Values => UnderlyingCollection.Values.OfType<K>().ToList();
        public bool IsReadOnly => UnderlyingCollection.IsReadOnly;
        public int Count => UnderlyingCollection.Count;
        public IDictionaryEnumerator GetEnumerator() => UnderlyingCollection.GetEnumerator();
        public void Insert(int index, T key, K value) => UnderlyingCollection.Insert(index, key, value);
        public void RemoveAt(int index) => UnderlyingCollection.RemoveAt(index);
        public bool Contains(T key) => UnderlyingCollection.Contains(key);
        public void Add(T key, K value) => UnderlyingCollection.Add(key, value);
        public void Clear() => UnderlyingCollection.Clear();
        public void Remove(T key) => UnderlyingCollection.Remove(key);
        public void CopyTo(Array array, int index) => UnderlyingCollection.CopyTo(array, index);
    }