How to change all values in a Dictionary<string, bool>?

Question

So I have a Dictionary<string, bool> and all I want to do is iterate over it and set all values to false in the dictionary. What is the easiest way to do that?

I tried this:

foreach (string key in parameterDictionary.Keys)
    parameterDictionary[key] = false;

However I get the error: "Collection was modified; enumeration operation may not execute."

Is there a better way to do this?

Solution 1

Just change the enumeration source to something other than the dictionary.

foreach (string key in parameterDictionary.Keys.ToList())
  parameterDictionary[key] = false;

---

For .net 2.0

foreach (string key in new List<TKey>(parameterDictionary.Keys))
  parameterDictionary[key] = false;

Solution 2

In .net 5 the following snippet no longer throws:

var d = new Dictionary<string, int> { { "a", 0 }, { "b", 0 }, { "c", 0 }};

foreach (var k in d.Keys){
      d[k] = 1;
}

Comments

[Chev]

Gah, it's always something so simple. Duh; it must be late. Thank you! Will accept in 12 minutes when I am able :)

[Rick Sladkey]

Unfortunately, this is not safe to do if keys are being added by a background thread.

[Amy B]

@kami ToList is an extension method defined on System.Linq.Enumerable, which is .net 3.5. You'll need to find another way to create an extra collection to use as an enumeration source.