System.Net.BigIntegerExtensions.ToBinaryString C# (CSharp) Method

        public static string ToBinaryString(this BigInteger bigint)
        {
            var bytes = bigint.ToByteArray();
            var idx = bytes.Length - 1;

            // Create a StringBuilder having appropriate capacity.
            var base2 = new StringBuilder(bytes.Length * 8);

            // Convert first byte to binary.
            var binary = Convert.ToString(bytes[idx], 2);

            // Ensure leading zero exists if value is positive.
            if (binary[0] != '0' && bigint.Sign == 1) {
                base2.Append('0');
            }

            // Append binary string to StringBuilder.
            base2.Append(binary);

            // Convert remaining bytes adding leading zeros.
            for (idx--; idx >= 0; idx--) {
                base2.Append(Convert.ToString(bytes[idx], 2).PadLeft(8, '0'));
            }

            return base2.ToString();
        }