Modify Dictionary values

Question

.NET 2

The standard:

  foreach(KeyValuePair<int,int> entry in MyDic)
  {
      entry.Value += i; // does not work :(
      i++;
  }

Recommendations?

Answer 1

Loop over the Keys property instead. When you use enumerators, any modification to the underlying collection invalidates the enumerator when it next calls MoveNext.

You can enumerate the Keys or AllKeys (which is just a string array) and modify the values they point to quite safely.

Also, the properties of KeyValuePair<K, V> are themselves read-only, so, iterator blocks or not, there's no circumstances under which you could modify those values without abusing reflection.