AudioManager.cs

using System;
using System.Runtime.InteropServices;
// ReSharper disable SuspiciousTypeConversion.Global
// ReSharper disable InconsistentNaming

namespace VideoPlayerController
{
    /// <summary>
    /// Controls audio using the Windows CoreAudio API
    /// from: http://stackoverflow.com/questions/14306048/controling-volume-mixer
    /// and: http://netcoreaudio.codeplex.com/
    /// </summary>
    public static class AudioManager
    {
        #region Master Volume Manipulation

        /// <summary>
        /// Gets the current master volume in scalar values (percentage)
        /// </summary>
        /// <returns>-1 in case of an error, if successful the value will be between 0 and 100</returns>
        public static float GetMasterVolume()
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return -1;

                float volumeLevel;
                masterVol.GetMasterVolumeLevelScalar(out volumeLevel);
                return volumeLevel*100;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Gets the mute state of the master volume. 
        /// While the volume can be muted the <see cref="GetMasterVolume"/> will still return the pre-muted volume value.
        /// </summary>
        /// <returns>false if not muted, true if volume is muted</returns>
        public static bool GetMasterVolumeMute()
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return false;

                bool isMuted;
                masterVol.GetMute(out isMuted);
                return isMuted;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Sets the master volume to a specific level
        /// </summary>
        /// <param name="newLevel">Value between 0 and 100 indicating the desired scalar value of the volume</param>
        public static void SetMasterVolume(float newLevel)
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return;

                masterVol.SetMasterVolumeLevelScalar(newLevel/100, Guid.Empty);
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Increments or decrements the current volume level by the <see cref="stepAmount"/>.
        /// </summary>
        /// <param name="stepAmount">Value between -100 and 100 indicating the desired step amount. Use negative numbers to decrease
        /// the volume and positive numbers to increase it.</param>
        /// <returns>the new volume level assigned</returns>
        public static float StepMasterVolume(float stepAmount)
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return -1;

                float stepAmountScaled = stepAmount/100;

                // Get the level
                float volumeLevel;
                masterVol.GetMasterVolumeLevelScalar(out volumeLevel);

                // Calculate the new level
                float newLevel = volumeLevel + stepAmountScaled;
                newLevel = Math.Min(1, newLevel);
                newLevel = Math.Max(0, newLevel);

                masterVol.SetMasterVolumeLevelScalar(newLevel, Guid.Empty);

                // Return the new volume level that was set
                return newLevel*100;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Mute or unmute the master volume
        /// </summary>
        /// <param name="isMuted">true to mute the master volume, false to unmute</param>
        public static void SetMasterVolumeMute(bool isMuted)
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return;

                masterVol.SetMute(isMuted, Guid.Empty);
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Switches between the master volume mute states depending on the current state
        /// </summary>
        /// <returns>the current mute state, true if the volume was muted, false if unmuted</returns>
        public static bool ToggleMasterVolumeMute()
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return false;

                bool isMuted;
                masterVol.GetMute(out isMuted);
                masterVol.SetMute(!isMuted, Guid.Empty);

                return !isMuted;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        private static IAudioEndpointVolume GetMasterVolumeObject()
        {
            IMMDeviceEnumerator deviceEnumerator = null;
            IMMDevice speakers = null;
            try
            {
                deviceEnumerator = (IMMDeviceEnumerator) (new MMDeviceEnumerator());
                deviceEnumerator.GetDefaultAudioEndpoint(EDataFlow.eRender, ERole.eMultimedia, out speakers);

                Guid IID_IAudioEndpointVolume = typeof (IAudioEndpointVolume).GUID;
                object o;
                speakers.Activate(ref IID_IAudioEndpointVolume, 0, IntPtr.Zero, out o);
                IAudioEndpointVolume masterVol = (IAudioEndpointVolume) o;

                return masterVol;
            }
            finally
            {
                if (speakers != null) Marshal.ReleaseComObject(speakers);
                if (deviceEnumerator != null) Marshal.ReleaseComObject(deviceEnumerator);
            }
        }

        #endregion
        
        #region Individual Application Volume Manipulation

        public static float? GetApplicationVolume(int pid)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return null;

            float level;
            volume.GetMasterVolume(out level);
            Marshal.ReleaseComObject(volume);
            return level*100;
        }

        public static bool? GetApplicationMute(int pid)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return null;

            bool mute;
            volume.GetMute(out mute);
            Marshal.ReleaseComObject(volume);
            return mute;
        }

        public static void SetApplicationVolume(int pid, float level)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return;

            Guid guid = Guid.Empty;
            volume.SetMasterVolume(level/100, ref guid);
            Marshal.ReleaseComObject(volume);
        }

        public static void SetApplicationMute(int pid, bool mute)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return;

            Guid guid = Guid.Empty;
            volume.SetMute(mute, ref guid);
            Marshal.ReleaseComObject(volume);
        }

        private static ISimpleAudioVolume GetVolumeObject(int pid)
        {
            IMMDeviceEnumerator deviceEnumerator = null;
            IAudioSessionEnumerator sessionEnumerator = null;
            IAudioSessionManager2 mgr = null;
            IMMDevice speakers = null;
            try
            {
                // get the speakers (1st render + multimedia) device
                deviceEnumerator = (IMMDeviceEnumerator) (new MMDeviceEnumerator());
                deviceEnumerator.GetDefaultAudioEndpoint(EDataFlow.eRender, ERole.eMultimedia, out speakers);

                // activate the session manager. we need the enumerator
                Guid IID_IAudioSessionManager2 = typeof (IAudioSessionManager2).GUID;
                object o;
                speakers.Activate(ref IID_IAudioSessionManager2, 0, IntPtr.Zero, out o);
                mgr = (IAudioSessionManager2) o;

                // enumerate sessions for on this device
                mgr.GetSessionEnumerator(out sessionEnumerator);
                int count;
                sessionEnumerator.GetCount(out count);

                // search for an audio session with the required process-id
                ISimpleAudioVolume volumeControl = null;
                for (int i = 0; i < count; ++i)
                {
                    IAudioSessionControl2 ctl = null;
                    try
                    {
                        sessionEnumerator.GetSession(i, out ctl);

                        // NOTE: we could also use the app name from ctl.GetDisplayName()
                        int cpid;
                        ctl.GetProcessId(out cpid);

                        if (cpid == pid)
                        {
                            volumeControl = ctl as ISimpleAudioVolume;
                            break;
                        }
                    }
                    finally
                    {
                        if (ctl != null) Marshal.ReleaseComObject(ctl);
                    }
                }

                return volumeControl;
            }
            finally
            {
                if (sessionEnumerator != null) Marshal.ReleaseComObject(sessionEnumerator);
                if (mgr != null) Marshal.ReleaseComObject(mgr);
                if (speakers != null) Marshal.ReleaseComObject(speakers);
                if (deviceEnumerator != null) Marshal.ReleaseComObject(deviceEnumerator);
            }
        }

        #endregion

    }

    #region Abstracted COM interfaces from Windows CoreAudio API

    [ComImport]
    [Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")]
    internal class MMDeviceEnumerator
    {
    }

    internal enum EDataFlow
    {
        eRender,
        eCapture,
        eAll,
        EDataFlow_enum_count
    }

    internal enum ERole
    {
        eConsole,
        eMultimedia,
        eCommunications,
        ERole_enum_count
    }

    [Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IMMDeviceEnumerator
    {
        int NotImpl1();

        [PreserveSig]
        int GetDefaultAudioEndpoint(EDataFlow dataFlow, ERole role, out IMMDevice ppDevice);

        // the rest is not implemented
    }

    [Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IMMDevice
    {
        [PreserveSig]
        int Activate(ref Guid iid, int dwClsCtx, IntPtr pActivationParams, [MarshalAs(UnmanagedType.IUnknown)] out object ppInterface);

        // the rest is not implemented
    }

    [Guid("77AA99A0-1BD6-484F-8BC7-2C654C9A9B6F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAudioSessionManager2
    {
        int NotImpl1();
        int NotImpl2();

        [PreserveSig]
        int GetSessionEnumerator(out IAudioSessionEnumerator SessionEnum);

        // the rest is not implemented
    }

    [Guid("E2F5BB11-0570-40CA-ACDD-3AA01277DEE8"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAudioSessionEnumerator
    {
        [PreserveSig]
        int GetCount(out int SessionCount);

        [PreserveSig]
        int GetSession(int SessionCount, out IAudioSessionControl2 Session);
    }

    [Guid("87CE5498-68D6-44E5-9215-6DA47EF883D8"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface ISimpleAudioVolume
    {
        [PreserveSig]
        int SetMasterVolume(float fLevel, ref Guid EventContext);

        [PreserveSig]
        int GetMasterVolume(out float pfLevel);

        [PreserveSig]
        int SetMute(bool bMute, ref Guid EventContext);

        [PreserveSig]
        int GetMute(out bool pbMute);
    }

    [Guid("bfb7ff88-7239-4fc9-8fa2-07c950be9c6d"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAudioSessionControl2
    {
        // IAudioSessionControl
        [PreserveSig]
        int NotImpl0();

        [PreserveSig]
        int GetDisplayName([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int SetDisplayName([MarshalAs(UnmanagedType.LPWStr)]string Value, [MarshalAs(UnmanagedType.LPStruct)] Guid EventContext);

        [PreserveSig]
        int GetIconPath([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int SetIconPath([MarshalAs(UnmanagedType.LPWStr)] string Value, [MarshalAs(UnmanagedType.LPStruct)] Guid EventContext);

        [PreserveSig]
        int GetGroupingParam(out Guid pRetVal);

        [PreserveSig]
        int SetGroupingParam([MarshalAs(UnmanagedType.LPStruct)] Guid Override, [MarshalAs(UnmanagedType.LPStruct)] Guid EventContext);

        [PreserveSig]
        int NotImpl1();

        [PreserveSig]
        int NotImpl2();

        // IAudioSessionControl2
        [PreserveSig]
        int GetSessionIdentifier([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int GetSessionInstanceIdentifier([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int GetProcessId(out int pRetVal);

        [PreserveSig]
        int IsSystemSoundsSession();

        [PreserveSig]
        int SetDuckingPreference(bool optOut);
    }

    // http://netcoreaudio.codeplex.com/SourceControl/latest#trunk/Code/CoreAudio/Interfaces/IAudioEndpointVolume.cs
    [Guid("5CDF2C82-841E-4546-9722-0CF74078229A"),InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IAudioEndpointVolume
    {
        [PreserveSig]
        int NotImpl1();

        [PreserveSig]
        int NotImpl2();

        /// <summary>
        /// Gets a count of the channels in the audio stream.
        /// </summary>
        /// <param name="channelCount">The number of channels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetChannelCount(
            [Out] [MarshalAs(UnmanagedType.U4)] out UInt32 channelCount);

        /// <summary>
        /// Sets the master volume level of the audio stream, in decibels.
        /// </summary>
        /// <param name="level">The new master volume level in decibels.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetMasterVolumeLevel(
            [In] [MarshalAs(UnmanagedType.R4)] float level,
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Sets the master volume level, expressed as a normalized, audio-tapered value.
        /// </summary>
        /// <param name="level">The new master volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetMasterVolumeLevelScalar(
            [In] [MarshalAs(UnmanagedType.R4)] float level,
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Gets the master volume level of the audio stream, in decibels.
        /// </summary>
        /// <param name="level">The volume level in decibels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetMasterVolumeLevel(
            [Out] [MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Gets the master volume level, expressed as a normalized, audio-tapered value.
        /// </summary>
        /// <param name="level">The volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetMasterVolumeLevelScalar(
            [Out] [MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Sets the volume level, in decibels, of the specified channel of the audio stream.
        /// </summary>
        /// <param name="channelNumber">The channel number.</param>
        /// <param name="level">The new volume level in decibels.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetChannelVolumeLevel(
            [In] [MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [In] [MarshalAs(UnmanagedType.R4)] float level,
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Sets the normalized, audio-tapered volume level of the specified channel in the audio stream.
        /// </summary>
        /// <param name="channelNumber">The channel number.</param>
        /// <param name="level">The new master volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetChannelVolumeLevelScalar(
            [In] [MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [In] [MarshalAs(UnmanagedType.R4)] float level,
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Gets the volume level, in decibels, of the specified channel in the audio stream.
        /// </summary>
        /// <param name="channelNumber">The zero-based channel number.</param>
		/// <param name="level">The volume level in decibels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetChannelVolumeLevel(
            [In] [MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [Out] [MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Gets the normalized, audio-tapered volume level of the specified channel of the audio stream.
        /// </summary>
        /// <param name="channelNumber">The zero-based channel number.</param>
		/// <param name="level">The volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetChannelVolumeLevelScalar(
            [In] [MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [Out] [MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Sets the muting state of the audio stream.
        /// </summary>
        /// <param name="isMuted">True to mute the stream, or false to unmute the stream.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetMute(
            [In] [MarshalAs(UnmanagedType.Bool)] Boolean isMuted,
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Gets the muting state of the audio stream.
        /// </summary>
        /// <param name="isMuted">The muting state. True if the stream is muted, false otherwise.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetMute(
            [Out] [MarshalAs(UnmanagedType.Bool)] out Boolean isMuted);

        /// <summary>
        /// Gets information about the current step in the volume range.
        /// </summary>
        /// <param name="step">The current zero-based step index.</param>
        /// <param name="stepCount">The total number of steps in the volume range.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetVolumeStepInfo(
            [Out] [MarshalAs(UnmanagedType.U4)] out UInt32 step,
            [Out] [MarshalAs(UnmanagedType.U4)] out UInt32 stepCount);

        /// <summary>
        /// Increases the volume level by one step.
        /// </summary>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int VolumeStepUp(
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Decreases the volume level by one step.
        /// </summary>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int VolumeStepDown(
            [In] [MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Queries the audio endpoint device for its hardware-supported functions.
        /// </summary>
        /// <param name="hardwareSupportMask">A hardware support mask that indicates the capabilities of the endpoint.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int QueryHardwareSupport(
            [Out] [MarshalAs(UnmanagedType.U4)] out UInt32 hardwareSupportMask);

        /// <summary>
        /// Gets the volume range of the audio stream, in decibels.
        /// </summary>
		/// <param name="volumeMin">The minimum volume level in decibels.</param>
		/// <param name="volumeMax">The maximum volume level in decibels.</param>
		/// <param name="volumeStep">The volume increment level in decibels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetVolumeRange(
            [Out] [MarshalAs(UnmanagedType.R4)] out float volumeMin,
            [Out] [MarshalAs(UnmanagedType.R4)] out float volumeMax,
            [Out] [MarshalAs(UnmanagedType.R4)] out float volumeStep);
    }

    #endregion
}

Perfect, work on Windows 10!!

I'm currently trying to get it running in one project. The whole thing runs on .NET-6 but I always get the exception (see above).
I don't know what could be the problem. I used it successfully under .NET 4.8 before. I didn't change anything, I copied the code and executed it...