Grundlæggende interop (P/Invoke) i overblik

using System;
using System.Runtime.InteropServices;

// Simple P/Invoke call to native Sleep (Windows kernel32)
// Note: This demo may only run on Windows, but it compiles everywhere.
public class Program
{
  [DllImport("kernel32.dll")]
  private static extern void Sleep(uint dwMilliseconds);

  public static void Main(string[] args)
  {
    Console.WriteLine("Sleeping for 200 ms...");
    // Call native function
    Sleep(200);
    Console.WriteLine("Awake!");
  }
}

using System;
using System.Runtime.InteropServices;

// Get system uptime (ms) from native function.
public class Program
{
  [DllImport("kernel32.dll")]
  private static extern ulong GetTickCount64();

  public static void Main(string[] args)
  {
    ulong ms = GetTickCount64();
    Console.WriteLine("Uptime (ms): " + ms);
  }
}

using System;
using System.Runtime.InteropServices;

// Demo: marshaling strings to Unicode with CharSet.Unicode.
// On non-Windows environments this may fail at runtime.
public class Program
{
  [DllImport("user32.dll", CharSet = CharSet.Unicode)]
  private static extern int MessageBox(IntPtr hWnd, string text, string caption, uint type);

  public static void Main(string[] args)
  {
    Console.WriteLine("Calling MessageBox (may require Windows GUI)...");
    // 0x00000040 = MB_ICONINFORMATION
    try
    {
      int result = MessageBox(IntPtr.Zero, "Hello from P/Invoke", "Interop", 0x00000040);
      Console.WriteLine("MessageBox returned: " + result);
    }
    catch (Exception ex)
    {
      Console.WriteLine("MessageBox failed at runtime: " + ex.GetType().Name);
    }
  }
}