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mciSendString (winmm)
The mciSendString function sends a command string to an MCI device. The device that the command is sent to is specified in the command string [This page was changed by iMpostoR]

C# Signature:

static extern Int32 mciSendString(string command, StringBuilder buffer, int bufferSize, IntPtr hwndCallback);

VB.NET Signature:

<DllImport("winmm.dll")> _
Private Shared Function mciSendString(ByVal command As String, ByVal buffer As StringBuilder, ByVal bufferSize As Integer, ByVal hwndCallback As IntPtr) As Integer
End Function

VB Signature:

Declare Ansi Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal command As String, ByRef buffer As StringBuilder, ByVal bufferSize As Integer, ByVal hWndCallback As IntPtr) As Integer



Tips & Tricks:

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Sample Code


// Open CD-ROM Drive Door
public void OpenCD()
    IntPtr ptr = IntPtr.Zero;
    StringBuilder returnstring = new StringBuilder();
    mciSendString("set CDAudio door open", returnstring,127, IntPtr.Zero);

// Open Media File
string sCommand = "open \"" + strFilePath + "\" type mpegvideo alias MediaFile";
mciSendString(sCommand, null, 0, 0);

// Play the Media File
sCommand = "play MediaFile notify";
// _frmObject is your form that will handle the notification messages
mciSendString(sCommand, null, 0, _frmObject.Handle.ToInt64());

// Declare the nofify constant
public const int MM_MCINOTIFY = 953;

// Override the WndProc function in the form
protected override void WndProc(ref Message m)
    if (m.Msg == MM_MCINOTIFY)
        // The file is done playing, do whatever

    base.WndProc(ref m);


' Open CD-ROM Drive Door
Public Sub OpenCDDoor()
     Dim returnstring As StringBuilder = New StringBuilder()
     mciSendString("set CDAudio door open", returnstring, 127, IntPtr.Zero)
End Sub

' Declare the notify constant
Public Const MM_MCINOTIFY As Integer = 953

' Open and play a media file
Public Sub OpenMediaFile(ByVal strFilePath As String)
     ' Open the media file
     Dim sCommand As String = "open """ + strFilePath + """ type waveaudio alias MediaFile"
     mciSendString(sCommand, Nothing, 0, IntPtr.Zero)

     ' It's is assumed this function is in a Form so Me points to the current instance of the form
     sCommand = "play MediaFile notify"
     mciSendString(sCommand, Nothing, 0, Me.Handle.ToInt64())
End Sub

' Override the WndProc function which is called when the play function ends
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
     If m.Msg = MM_MCINOTIFY Then
     ' The file is done playing, do whatever is necessary at this point
     MsgBox("Done playing.")
     End If
End Sub

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