C# BitConverte扩展方法，提供基于大端模式下的数值和字节数组的相互转换

数值转字节数组，以及字节数组转数值，需要注意的是C#的本地字节序是小端模式的，而网络字节序却是（大端模式），所以我用到了IPAddress来进行Host和Network的转换

为了简单以及更好的性能，做了一些取巧的处理方式，尽量避免数组拷贝和反转，看上去很诡异，但是经过测试貌似没啥问题，不敢保证百分百没问题啊，如果有问题，望指出啊

/// <summary>
    /// 对BitConverter进行方法扩展
    /// </summary>
    public static class BitConverterExtend {
        /// <summary>
        /// 得到数值的网络字节序（大端模式）的字节数组
        /// </summary> 
        public static byte[] GetBytes_Network(this short num) {
            return BitConverter.GetBytes(IPAddress.HostToNetworkOrder(num));
        }
        public static byte[] GetBytes_Network(this ushort num) {
            return ((short)num).GetBytes_Network();  //这样比反转数组快
        }
        public static byte[] GetBytes_Network(this int num) {
            return BitConverter.GetBytes(IPAddress.HostToNetworkOrder(num));
        }
        public static byte[] GetBytes_Network(this uint num) {
            return ((int)num).GetBytes_Network();
        }
        public static byte[] GetBytes_Network(this long num) {
            return BitConverter.GetBytes(IPAddress.HostToNetworkOrder(num));
        }
        public static byte[] GetBytes_Network(this ulong num) {
            return ((long)num).GetBytes_Network();
        }
        public static byte[] GetBytes_Network(this float num) {
            return ((int)num).GetBytes_Network();  //字节数组是一样的，避免创建新的数组容器以及反转数组
        }
        public static byte[] GetBytes_Network(this double num) {
            return ((long)num).GetBytes_Network();
        }
        public static byte[] GetBytes_UTF8(this string value) {
            return Encoding.UTF8.GetBytes(value);
        }
        /// <summary>
        /// 将网络字节序（大端模式）的字节数组转成本地字节序（小端模式）的数值
        /// </summary> 
        public static short ToInt16_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return IPAddress.NetworkToHostOrder(BitConverter.ToInt16(networkBytes, startIndex));  //传入引用和起始索引，减少一个数组拷贝
        }
        public static ushort ToUInt16_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return (ushort)((networkBytes[startIndex++] << 8) | networkBytes[startIndex]); //直接自己按位操作，这样最快
        }
        public static int ToInt32_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return IPAddress.NetworkToHostOrder(BitConverter.ToInt32(networkBytes, startIndex));
        }
        public static uint ToUInt32_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return (uint)((networkBytes[startIndex++] << 24) | (networkBytes[startIndex++] << 16)
                | (networkBytes[startIndex++] << 8) | networkBytes[startIndex]);
        }
        public static long ToInt64_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return IPAddress.NetworkToHostOrder(BitConverter.ToInt64(networkBytes, startIndex));
        }
        public static ulong ToUInt64_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return (ulong)((networkBytes[startIndex++] << 56) | (networkBytes[startIndex++] << 48)
                | (networkBytes[startIndex++] << 40) | (networkBytes[startIndex++] << 32)
                | (networkBytes[startIndex++] << 24) | (networkBytes[startIndex++] << 16)
                | (networkBytes[startIndex++] << 8) | networkBytes[startIndex]);
        }
        public static float ToFloat_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return networkBytes.ToInt32_ByNetworkBytes(startIndex);  //int能隐式转换成float
        }
        public static double ToDouble_ByNetworkBytes(this byte[] networkBytes, int startIndex) {
            return networkBytes.ToInt64_ByNetworkBytes(startIndex);
        }
        public static string GetString_UTF8(this byte[] value, int startIndex, int count) {
            return Encoding.UTF8.GetString(value, startIndex, count);
        }
    }