Enumerating Sound Recording Devices (Using winmm.dll/C#)

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Introduction

This article describes a sample class that uses winmm.dll in C# through P/Invoke to enumerate sound recording devices.

Using the code

Let's start by including all the namespaces we are going to use:

using System.Runtime.InteropServices;//DLLimport
using System.Collections;//arrayList

The second step is declaring all the APIs we need:

//return total Sound Recording Devices
[DllImport("winmm.dll")]
public static extern int waveInGetNumDevs();
//return spesific Sound Recording Devices spec
[DllImport("winmm.dll", EntryPoint = "waveInGetDevCaps")]
public static extern int waveInGetDevCapsA(int uDeviceID, ref WaveInCaps lpCaps, int uSize);

The third step is to declare the "WaveInCaps" struct returned by the waveInGetDevCaps API. I found this one in "http://www.dotnetjunkies.com/WebLog/debasish/archive/2006/11/25/160495.aspx" - thanks to "debasish" for the hard work.

[StructLayout(LayoutKind.Sequential, Pack = 4)]
public struct WaveInCaps
{
    public short wMid;
    public short wPid;
    public int vDriverVersion;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
    public char[] szPname;
    public uint dwFormats;
    public short wChannels;
    public short wReserved1;
}

From here, it's just straightforward C# coding...

I implemented this in a clsRecDevices class:

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Collections;
namespace winApp
{
class clsRecDevices
{ 
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct WaveInCaps
    {
        public short wMid;
        public short wPid;
        public int vDriverVersion;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
        public char[] szPname;
        public uint dwFormats;
        public short wChannels;
        public short wReserved1;
    } 

    [DllImport("winmm.dll")]
    public static extern int waveInGetNumDevs();
    [DllImport("winmm.dll", EntryPoint = "waveInGetDevCaps")]
    public static extern int waveInGetDevCapsA(int uDeviceID, 
                         ref WaveInCaps lpCaps, int uSize);
    ArrayList arrLst = new ArrayList();
    //using to store all sound recording devices strings 

    public int Count
    //to return total sound recording devices found
    { 
        get {return arrLst.Count;}
    }
    public string this[int indexer]
    //return spesipic sound recording device name
    {
        get{return (string)arrLst[indexer];}
    }
    public clsRecDevices() //fill sound recording devices array
    {
        int waveInDevicesCount = waveInGetNumDevs(); //get total
        if (waveInDevicesCount > 0)
        {
            for (int uDeviceID = 0; uDeviceID < waveInDevicesCount; uDeviceID++)
            {
                WaveInCaps waveInCaps = new WaveInCaps();
                waveInGetDevCapsA(uDeviceID,ref waveInCaps, 
                                  Marshal.SizeOf(typeof(WaveInCaps))); 
                arrLst.Add(new string(waveInCaps.szPname).Remove(
                           new string(waveInCaps.szPname).IndexOf('\0')).Trim());
                           //clean garbage
            }
        }
    } 
}
}

This class can be used as follows:

clsRecDevices recDev = new clsRecDevices();
for (int i = 0; i < recDev.Count; i++){
    MessageBox.Show(recDev[i]);
}

History

You can also implement IEnumerator and IEnumerable to add some cool indexing features.