Unique Path using DP (c#)

[ssp2503]

public int UniquePaths(int m, int n) {
         var dp = new int[m,n];

            for (int i = m - 1; i >= 0; i--)
            {
                for (int j = n - 1; j >= 0; j--)
                {
                    if (i == m - 1 || j == n - 1)
                    {
                        dp[i, j] = 1;
                    }
                    else
                    {
                        dp[i, j] = dp[i + 1, j] + dp[i, j + 1];
                    }
                }
            }

            return dp[0, 0];
    }