Question

I’m trying to update a hashtable in a loop but getting an error: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.

private Hashtable htSettings_m = new Hashtable(); htSettings_m.Add('SizeWidth', '728'); htSettings_m.Add('SizeHeight', '450'); string sKey = ''; string sValue = ''; foreach (DictionaryEntry deEntry in htSettings_m) {     // Get value from Registry and assign to sValue.     // ...     // Change value in hashtable.     sKey = deEntry.Key.ToString();     htSettings_m[sKey] = sValue; } 

Is there way around it or maybe there is a better data structure for such purpose?

Answer 1

you could read the collection of keys into another IEnumerable instance first, then foreach over that list

        System.Collections.Hashtable ht = new System.Collections.Hashtable();          ht.Add('test1', 'test2');         ht.Add('test3', 'test4');          List<string> keys = new List<string>();         foreach (System.Collections.DictionaryEntry de in ht)             keys.Add(de.Key.ToString());          foreach(string key in keys)         {             ht[key] = DateTime.Now;             Console.WriteLine(ht[key]);         }