How to turn byte[] into sbyte* in C#?

Question

I have a function that want to receive sbyte* buffer how to create such in C# from scratch and from existing byte[]?

Answer 1

// Allocate a new buffer (skip this if you already have one)
byte[] buffer = new byte[256];
unsafe
{
    // The "fixed" statement tells the runtime to keep the array in the same
    // place in memory (relocating it would make the pointer invalid)
    fixed (byte* ptr_byte = &buffer[0])
    {
        // Cast the pointer to sbyte*
        sbyte* ptr_sbyte = (sbyte*) ptr_byte;

        // Do your stuff here
    }

    // The end of the "fixed" block tells the runtime that the original array
    // is available for relocation and/or garbage collection again
}

Answer 2

Casting to Array and then casting to byte[] will be enough.

byte[] unsigned = { 0, 1, 2 };

sbyte[] signed = (sbyte[]) (Array)unsigned;