Monday, June 29, 2009

Win32 Api Calls from C#

Here I am demonstrating opening and closing the CD Rom Drive using the win32 api with c#.
This was one of my favourite progam in VB era and so I thought of migrating it to C#.
mciSendString encapsulates the Media Control Interface developed by Microsoft and IBM for controlling the peripherals connected to Windows.

It's better to encapsulate the Win32 api inside a class library. So from the Windows Forms Application add a class library.

using System.Runtime.InteropServices;

namespace OpenCDWindow
class OpenCDDoor
[DllImport("winmm.dll", EntryPoint = "mciSendStringA")]
public static extern void mciSendStringA(string lpstrCommand,
string lpstrReturnString, long uReturnLength, long hwndCallback);

Back in the windows forms you can call the win32 api that you have declared in the class.

string rt = "";
private void btnOpen_Click(object sender, EventArgs e)
OpenCDDoor.mciSendStringA("set CDAudio door open", rt, 127, 0);
private void btnClose_Click(object sender, EventArgs e)
OpenCDDoor.mciSendStringA("set CDAudio door closed", rt, 127, 0);

VB 6
Public Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Long, ByVal hwndCallback As Long) As Long

Private Sub CmdClose_Click()
mciSendString "set CDAudio door closed", returnstring, 1, 0
End Sub

Private Sub CmdOpen_Click()
mciSendString "set CDAudio door open", returnstring, 1, 0
End Sub

AnimateWindow Win32 Api
Now we will take up a slightly more complex api which takes a few constatnts.
The AnimateWindow function enables you to produce special effects.
using System.Runtime.InteropServices;

const uint AW_HOR_NEGATIVE = 2;
const uint AW_VER_POSITIVE = 4;
const uint AW_HIDE = 0x10000;

static extern bool AnimateWindow(IntPtr hWnd, UInt32 time, UInt32 flags);

private void btnAnimate_Click(object sender, EventArgs e)
AnimateWindow(this.Handle, 1000, AW_VER_POSITIVE AW_HOR_NEGATIVE AW_HIDE);

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