Implements finding longest palindrome in a string using dynamic programming in C#.

LongestPalindrome.cs

public static string LongestPalindrome(string str) 
{
    var chars = str.ToCharArray();
    var dp = new bool[chars.Length, chars.Length];
    int longestBegin = 0;
    int maxLength = 1;
    for (int i = 0; i < chars.Length; i++)
    {
        dp[i, i] = true;
    }
    for (int i = 0; i < chars.Length-1; i++)
    {
        if(chars[i] == chars[i+1])
        {
            dp[i, i+1] = true;
            longestBegin = i;
            maxLength = 2;
        }
    }
    for (int length = 3; length <= chars.Length; length++)
    {
        for (int i = 0; i < chars.Length-length+1; i++)
        {
            int j = i+length-1;
            if(chars[i] == chars[j] && dp[i+1, j-1])
            {
                dp[i, j] = true;
                if(maxLength < (j-i))
                {
                    maxLength = j - i;
                    longestBegin = i;
                }
            }
        }
    }
    return str.Substring(longestBegin, maxLength);
}