How to check if the system audio is muted?

I found this answer which recommends using the "core audio.dll" API with the following code:

private function getmute() as boolean
    Dim devenum As New MMDeviceEnumerator
    Dim device As MMDevice = devenum.GetDefaultAudioEndpoint(EDataFlow.eRender, ERole.eMultimedia)
    If device.AudioEndpointVolume.Mute = True Then
        Return True
    Else
        Return False
    End If
End Function

I tried that code but it doesn't work and I could not leave a comment on the other question.

When I try the above code, the following line throws an exception:

If device.AudioEndpointVolume.Mute = True Then

Here's the exception message:

AudioEndpointVolume is not a member of device.

I have already imported CoreAudioAPI, what else could be wrong?

I'm looking for a VB.NET or a C# solution.

Solution

VB.Net rewriting (+ Bonus) of the CoreAudio API implementation γηράσκω δ' αεί πολλά διδασκόμε posted.

The code in wrapped in a Class (AudioDevice) and includes the original IsMuted() method, plus other methods I implemented on the fly (because, why not).

More information on the Windows CoreAudio APIs on MSDN.
GitHub NAudio CoreAudioApi implementation (C#).

Methods implemented:

IsMuted() As Integer
Return the Muted status of the default Audio Device.

SetMute(Boolean)
Sets the Muted status of the default Audio Device (True/False)

IsMediadPlaying() The default Audio Device is currently playing or not

GetVolume() As Integer
Get the Volume status of the default Audio Device. Values range from 0 to 100

SetVolume(Integer)
Set the Volume status of the default Audio Device to a values in the 0 to 100 range

VolumeUp()
Increases the Volume of the default Audio Device by one step (usually 2 units)

VolumeDown()
Decreases the Volume of the default Audio Device by one step.

Usage:

 Dim isMuted As Boolean = AudioDevice.IsMuted()

 ' True=Mutes the Audio, False=Un-Mutes (?) it
 AudioDevice.SetMute(True)

 ' Checks whether the Media Device currently playing
 Dim isPlaying As Boolean = AudioDevice.IsMediadPlaying()

 Dim volume As Integer = AudioDevice.GetVolume()

 ' Sets the Audio level to 50%, returns the previous value
 Dim previousVolume As Integer = AudioDevice.SetVolume(50)

 ' Increases the Audio level by 1 Step
 AudioDevice.VolumeUp()

 ' Decreases the Audio level by 1 Step
 AudioDevice.VolumeDown()

Declarations:

Imports System
Imports System.Runtime.InteropServices

Public Class AudioDevice
    Friend Enum EDataFlow
        eRender
        eCapture
        eAll
        EDataFlow_enum_count
    End Enum

    Friend Enum ERole
        eConsole
        eMultimedia
        eCommunications
        ERole_enum_count
    End Enum

    <Flags>
    Public Enum CLSCTX As UInteger
        CLSCTX_INPROC_SERVER = &H1
        CLSCTX_INPROC_HANDLER = &H2
        CLSCTX_LOCAL_SERVER = &H4
        CLSCTX_INPROC_SERVER16 = &H8
        CLSCTX_REMOTE_SERVER = &H10
        CLSCTX_INPROC_HANDLER16 = &H20
        CLSCTX_RESERVED1 = &H40
        CLSCTX_RESERVED2 = &H80
        CLSCTX_RESERVED3 = &H100
        CLSCTX_RESERVED4 = &H200
        CLSCTX_NO_CODE_DOWNLOAD = &H400
        CLSCTX_RESERVED5 = &H800
        CLSCTX_NO_CUSTOM_MARSHAL = &H1000
        CLSCTX_ENABLE_CODE_DOWNLOAD = &H2000
        CLSCTX_NO_FAILURE_LOG = &H4000
        CLSCTX_DISABLE_AAA = &H8000
        CLSCTX_ENABLE_AAA = &H10000
        CLSCTX_FROM_DEFAULT_CONTEXT = &H20000
        CLSCTX_ACTIVATE_32_BIT_SERVER = &H40000
        CLSCTX_ACTIVATE_64_BIT_SERVER = &H80000
        CLSCTX_INPROC = CLSCTX_INPROC_SERVER Or CLSCTX_INPROC_HANDLER
        CLSCTX_SERVER = CLSCTX_INPROC_SERVER Or CLSCTX_LOCAL_SERVER Or CLSCTX_REMOTE_SERVER
        CLSCTX_ALL = CLSCTX_SERVER Or CLSCTX_INPROC_HANDLER
    End Enum

    <ComImport, Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")>
    Public Class MMDeviceEnumeratorComObject
    End Class

    <ComImport, Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)>
    Friend Interface IMMDeviceEnumerator
        Function NotImpl1() As Integer
        Function GetDefaultAudioEndpoint(
              dataFlow As EDataFlow,
              role As ERole,
              <Out> ByRef ppDevice As IMMDevice) As Integer
    End Interface

    <ComImport, Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)>
    Public Interface IMMDevice
        Function Activate(<MarshalAs(UnmanagedType.LPStruct)> iid As Guid,
                          dwClsCtx As CLSCTX, pActivationParams As IntPtr) As <MarshalAs(UnmanagedType.IUnknown)> Object
    End Interface

    <ComImport, Guid("5CDF2C82-841E-4546-9722-0CF74078229A"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)>
    Public Interface IAudioEndpointVolume
        Function RegisterControlChangeNotify(pNotify As IAudioEndpointVolumeCallback) As Integer
        Function UnregisterControlChangeNotify(pNotify As IAudioEndpointVolumeCallback) As Integer
        Function GetChannelCount(ByRef channelCount As Integer) As Integer
        Function SetMasterVolumeLevel() As Integer
        Function SetMasterVolumeLevelScalar(level As Single, eventContext As Guid) As Integer
        Function GetMasterVolumeLevel(<Out> ByRef level As Single) As Integer
        Function GetMasterVolumeLevelScalar(<Out> ByRef level As Single) As Integer
        Function SetChannelVolumeLevel(channelNumber As Integer, level As Single, eventContext As Guid) As Integer
        Function SetChannelVolumeLevelScalar(channelNumber As Integer, level As Single, eventContext As Guid) As Integer
        Function GetChannelVolumeLevel(channelNumber As Integer, <Out> ByRef level As Single) As Integer
        Function GetChannelVolumeLevelScalar(channelNumber As Integer, <Out> ByRef level As Single) As Integer
        Function SetMute(<MarshalAs(UnmanagedType.Bool)> isMuted As Boolean, eventContext As Guid) As Integer
        Function GetMute(<Out> ByRef isMuted As Boolean) As Integer
        Function GetVolumeStepInfo(<Out> ByRef pnStep As Integer, ByRef pnStepCount As Integer) As Integer
        Function VolumeStepUp(eventContext As Guid) As Integer
        Function VolumeStepDown(eventContext As Guid) As Integer
        Function QueryHardwareSupport(<Out> ByRef hardwareSupportMask As Integer) As Integer
        Function GetVolumeRange(<Out> ByRef volumeMin As Single, <Out> ByRef volumeMax As Single, <Out> ByRef volumeStep As Single) As Integer
    End Interface

    <ComImport, Guid("657804FA-D6AD-4496-8A60-352752AF4F89"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)>
    Public Interface IAudioEndpointVolumeCallback
        <PreserveSig()>
        Function OnNotify(pNotifyData As IntPtr) As Integer  ' HRESULT
    End Interface

    <InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("C02216F6-8C67-4B5B-9D00-D008E73E0064")>
    Public Interface IAudioMeterInformation
        Function GetPeakValue() As Single
    End Interface

    Public Shared Function IsMuted() As Boolean
        Dim masterVol As IAudioEndpointVolume = GetMasterVolumeObject()
        Try
            If masterVol Is Nothing Then
                Throw New ApplicationException("Master Volume not available")
            End If

            Dim isAudioMuted As Boolean
            masterVol.GetMute(isAudioMuted)
            Return isAudioMuted
        Finally
            If masterVol IsNot Nothing Then
                If masterVol IsNot Nothing Then Marshal.ReleaseComObject(masterVol)
            End If
        End Try
    End Function

    Public Shared Sub SetMute(IsMute As Boolean)
        Dim masterVol As IAudioEndpointVolume = GetMasterVolumeObject()
        Try
            masterVol.SetMute(IsMute, Guid.Empty)
        Finally
            If masterVol IsNot Nothing Then
                If masterVol IsNot Nothing Then Marshal.ReleaseComObject(masterVol)
            End If
        End Try
    End Sub

    Public Shared Function IsMediadPlaying() As Boolean
        Dim mediaDevice As IMMDevice = Nothing
        Try
            mediaDevice = GetDefaultAudioEndpoint()
            Dim meter = mediaDevice.Activate(GetType(IAudioMeterInformation).GUID, CLSCTX.CLSCTX_ALL, IntPtr.Zero)
            Dim value As Single = DirectCast(meter, IAudioMeterInformation).GetPeakValue()
            Return Not (value <= 0.0F)
        Finally
            If mediaDevice IsNot Nothing Then Marshal.ReleaseComObject(mediaDevice)
        End Try
    End Function

    Public Shared Function GetVolume() As Integer
        Dim fVolume As Single
        Dim masterVol As IAudioEndpointVolume = GetMasterVolumeObject()
        Try
            masterVol.GetMasterVolumeLevelScalar(fVolume)
            Return CType(fVolume * 100, Integer)
        Finally
            If masterVol IsNot Nothing Then Marshal.ReleaseComObject(masterVol)
        End Try
    End Function

    Public Shared Function SetVolume(volume As Integer) As Integer
        volume = Math.Max(Math.Min(volume, 100), 0)
        Dim masterVolume As IAudioEndpointVolume = GetMasterVolumeObject()
        Try
            Dim prevVolume = GetVolume()
            masterVolume.SetMasterVolumeLevelScalar(volume / 100.0F, Guid.Empty)
            Return prevVolume
        Finally
            If masterVolume IsNot Nothing Then Marshal.ReleaseComObject(masterVolume)
        End Try
    End Function

    Public Shared Sub VolumeUp()
        Dim masterVol As IAudioEndpointVolume = GetMasterVolumeObject()
        Try
            masterVol.VolumeStepUp(Guid.Empty)
        Finally
            If masterVol IsNot Nothing Then Marshal.ReleaseComObject(masterVol)
        End Try
    End Sub

    Public Shared Sub VolumeDown()
        Dim masterVol As IAudioEndpointVolume = GetMasterVolumeObject()
        Try
            masterVol.VolumeStepDown(Guid.Empty)
        Finally
            If masterVol IsNot Nothing Then Marshal.ReleaseComObject(masterVol)
        End Try
    End Sub

    Friend Shared Function GetMasterVolumeObject() As IAudioEndpointVolume
        Dim mediaDevice As IMMDevice = GetDefaultAudioEndpoint()
        Try
            Dim ppEndpoint = mediaDevice.Activate(GetType(IAudioEndpointVolume).GUID, CLSCTX.CLSCTX_ALL, IntPtr.Zero)
            Return DirectCast(ppEndpoint, IAudioEndpointVolume)
        Finally
            If mediaDevice IsNot Nothing Then Marshal.ReleaseComObject(mediaDevice)
        End Try
    End Function

    Public Shared Function GetDefaultAudioEndpoint() As IMMDevice
        Dim mediaDevice As IMMDevice = Nothing
        Dim deviceEnumerator = DirectCast(New MMDeviceEnumeratorComObject(), IMMDeviceEnumerator)
        Try
            deviceEnumerator.GetDefaultAudioEndpoint(EDataFlow.eRender, ERole.eMultimedia, mediaDevice)
            Return mediaDevice
        Finally
            If deviceEnumerator IsNot Nothing Then Marshal.ReleaseComObject(deviceEnumerator)
        End Try
    End Function
End Class