changing values of dictionary keys

Question

I had a list of strings.

I wanted to delete one in it as follows:

  settings.RecentSearches.Keys.Remove(itemToAdd.Key);
  settings.RecentSearches.Keys.Add(itemToAdd.Key);

Error:

Mutating a key collection derived from a dictionary is not allowed.

I wanted to add and delete values in it.

What can i do?

What type of RecentSearches property? – Sergey Litvinov Dec 26 '13 at 13:02 — Sergey Litvinov, Dec 26 '13 at 13:02
@SergeyLitvinov public MruDictionary RecentSearches; – C Sharper Dec 26 '13 at 13:02 — C Sharper, Dec 26 '13 at 13:02

score 7 · Accepted Answer · answered Dec 26 '13 at 13:03

7

You can't remove an item from the collection of keys of a dictionary. You have to remove the item from the dictionary itself using Dictionary.Remove.

answered Dec 26 '13 at 13:03

ken2k

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but it does not get removed from key – C Sharper Dec 26 '13 at 13:05
2

@LOLSinger It does. If you remove an item from the dictionary, the associated key will be removed too. – ken2k Dec 26 '13 at 13:07
thanx sir, it removed the key – C Sharper Dec 26 '13 at 13:15

score 2 · Answer 2 · answered Dec 26 '13 at 13:12

Remove

settings.RecentSearches.Remove(itemToAdd.Key);

Add settings.RecentSearches[itemToAdd.Key] = itemToAdd.Value;

This will add the key to the dictionary if the key already not exists. If the key already exists, the value will be overwritten. To avoid, overwriting, have a if check.

score 1 · Answer 3 · answered Dec 26 '13 at 13:10

Well i'm not C# background guy. I suggest you one of the idea that may help you,

Create dictionary class category or subclass of dictionary.
Save your key value in temporary variable.
Remove your key from dictionary directly.
Add your new key and set your temporary variable saved value under that key.

score 1 · Answer 4 · answered Dec 26 '13 at 13:10

1

The problem is you are using Keys.Add and Keys.Remove, not the .Add and .Remove methods of the Dictionary itself.

settings.RecentSearches.Remove(itemToAdd.Key);
settings.RecentSearches.Add(itemToAdd.Key);

answered Dec 26 '13 at 13:10

Boluc Papuccuoglu

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changing values of dictionary keys

4 Answers4