LeetCode -- Longest Palindrome

public class Solution {    public int LongestPalindrome(string s) {        if(string.IsNullOrWhiteSpace(s)){    		return 0;    	}    	    	var dict = new Dictionary<char, int>();    	    	var len = s.Length;    	for (var i = 0;i < len; i++){    		if(!dict.ContainsKey(s[i])){    			dict.Add(s[i], 1);    		}    		else{    			dict[s[i]] ++;    		}    	}    	    	int maxLen = 0;    	bool hasMid = false;    	foreach (var k in dict.Keys){    		if(dict[k] % 2 == 0){    			maxLen += dict[k];    		}else{    			hasMid = true;    			if(dict[k] - 1 > 1){    				maxLen += dict[k] - 1;    			}    		}    	}    	    	if(hasMid){    		maxLen ++;    	}    	    	return maxLen;    }}