409.求最长回文串的长度 LongestPalindrome

public static int LongestPalindrome(string s) {
	int length = 0;
	Dictionary<char, int> dictionary = new Dictionary<char, int>();
	int value = 0;
	foreach (char c in s) {
		if (dictionary.TryGetValue(c, out value)) {
			dictionary[c]+=1;
		} else {
			dictionary[c] = 1;
		}
	}
	bool addCenter = false;
	foreach (int val in dictionary.Values) {
		if (addCenter == false && val % 2 != 0) {
			length++;
			addCenter = true;
		}
		if (val > 1) {
			length += (val - val % 2);
		} 
	}
	return length;
}