execute-byte-array.cs

using System.Runtime.InteropServices;
using System;

public static unsafe class Program
{
    [DllImport("kernel32.dll")]
    private static extern void* VirtualAlloc(void* addr, int size, int type, int protect);
    [DllImport("kernel32.dll")]
    private static extern bool VirtualProtect(void* addr, int size, int new_protect, int* old_protect);
    [DllImport("kernel32.dll")]
    private static extern bool VirtualFree(void* addr, int size, int type);

    public static int Main(string[] argv)
    {
        byte[] asm = {
            0x8D, 0x04, 0x11,   // lea eax, [rcx+rdx]
            0xC3                // ret
        };

        void* buffer = VirtualAlloc(null, asm.Length, 0x1000, 4);
        var func = (delegate*<int, int, int>)buffer;
        int dummy;

        Marshal.Copy(asm, 0, (nint)buffer, asm.Length);
        VirtualProtect(buffer, asm.Length, 0x20, &dummy);

        Console.WriteLine(func(42, 378)); // call 'func' with (42, 378), which computes '420'

        VirtualFree(buffer, 0, 0x8000);
    }
}

Beautiful code. Thanks

@Mshriver2 thanks. You're welcome.

Please note though that it is only a proof-of-concept and that this code might not be applicable in many other contexts....