Question

I’m using a Dictionary<int, KeyValuePair<bool, int>> to hold data.

From time to time I need to increment the int in the KeyValuePair, but it won’t let me, because it has no setter. Is there a way to increment it?

Code sample:

Dictionary<int, KeyValuePair<bool, int>> mDictionary = 
    new Dictionary<int, KeyValuePair<bool, int>>();

mDictionary[trapType].Value++;
//Error: The property KeyValuePair<TKey, Tvalue>>.Value has no setter

Answer 1

Is there a way to increment it?

No. KeyValuePair is immutable – it’s also a value type, so changing the value of the Value property after creating a copy wouldn’t help anyway.

You’d have to write something like this:

var existingValue = mDictionary[trapType];
var newValue = new KeyValuePair<bool, int>(existingValue.Key,
                                           existingValue.Value + 1);
mDictionary[trapType] = newValue;

It’s pretty ugly though – do you really need the value to be a KeyValuePair?