How to update value of a key in dictionary in c#? [duplicate]

Question

I have the following code in c# , basically it's a simple dictionary with some keys and their values.

Dictionary<string, int> dictionary =     new Dictionary<string, int>(); dictionary.Add("cat", 2); dictionary.Add("dog", 1); dictionary.Add("llama", 0); dictionary.Add("iguana", -1); 

I want to update the key 'cat' with new value 5.
How could I do this?

Answer 1

Have you tried just

dictionary["cat"] = 5; 

:)

Update

dictionary["cat"] = 5+2; dictionary["cat"] = dictionary["cat"]+2; dictionary["cat"] += 2; 

Beware of non-existing keys :)

Answer 2

Try this simple function to add an dictionary item if it does not exist or update when it exists:

    public void AddOrUpdateDictionaryEntry(string key, int value)     {         if (dict.ContainsKey(key))         {             dict[key] = value;         }         else         {             dict.Add(key, value);         }     } 

This is the same as dict[key] = value.