C# - 将 Int 转换为 Hex 4 字节

Question

I want to convert an int to hex 4 bytes.

I use this:

int a = 50;
a.ToString("X8");

This return "00000032".

But i want to return "0x00, 0x00, 0x00, 0x32".

Thanks for help.

Answer 1

This is an area where you need to be very careful about "endianness"; in most simple scenarios, your best bet is to use shift operations, ie

static void Main()
{
    static string ByteHex(int value) => (value & 0xFF).ToString("X2");
    int a = 50;
    Console.WriteLine("0x" + ByteHex(a >> 24));
    Console.WriteLine("0x" + ByteHex(a >> 16));
    Console.WriteLine("0x" + ByteHex(a >> 8));
    Console.WriteLine("0x" + ByteHex(a));
}

In more nuanced cases, there is a new-ish BinaryPrimitives type that is your friend:

int a = 50;
Span<byte> span = stackalloc byte[4];
BinaryPrimitives.WriteInt32BigEndian(span, a);
// now access span[0] - span[3]

This is usually preferable to BitConverter which a: is allocation-heavy, and b: is awkward re endianness (you need to flip on BitConverter.IsLittleEndian )

Answer 2

This should do the job:

int a = 50;

string result = string.Join(", ", BitConverter.GetBytes(a).Reverse().Select(b => "0x" + b.ToString("X2")));

Console.WriteLine(result);