namespace System.Web.ModelBinding {
    using System;
    using System.Collections.Generic;
    using System.Linq;
 
    internal static class DictionaryHelpers {
 
        public static IEnumerable<KeyValuePair<string, TValue>> FindKeysWithPrefix<TValue>(IDictionary<string, TValue> dictionary, string prefix) {
            TValue exactMatchValue;
            if (dictionary.TryGetValue(prefix, out exactMatchValue)) {
                yield return new KeyValuePair<string, TValue>(prefix, exactMatchValue);
            }
 
            foreach (var entry in dictionary) {
                string key = entry.Key;
 
                if (key.Length <= prefix.Length) {
                    continue;
                }
 
                if (!key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)) {
                    continue;
                }
 
                char charAfterPrefix = key[prefix.Length];
                switch (charAfterPrefix) {
                    case '[':
                    case '.':
                        yield return entry;
                        break;
                }
            }
        }
 
        public static bool DoesAnyKeyHavePrefix<TValue>(IDictionary<string, TValue> dictionary, string prefix) {
            return FindKeysWithPrefix(dictionary, prefix).Any();
        }
 
    }
}