Dynamic programming in C#

public int ClimbStairs(int n) {
    if (n <= 1) return 1;
    int[] dp = new int[n + 1];
    dp[0] = 1;
    dp[1] = 1;

    for (int i = 2; i <= n; i++) {
        dp[i] = dp[i - 1] + dp[i - 2];
    }

    return dp[n];
}