需要知道的

調音量是可以快捷鍵的，還可以用Winmm.dll，但是這個過於複雜了，還有左右聲道，我們不需要這麼複雜。還有個辦法

https://stackoverflow.com/questions/14306048/controlling-volume-mixer

程式碼

public static class SystemVolume
{
#region Master Volume Manipulation

/// <summary>
/// 返回系統音量(1~100)
/// </summary>
public static float GetMasterVolume()
{
IAudioEndpointVolume masterVol 
 
= null;
try
{
    masterVol = GetMasterVolumeObject();
    if (masterVol == null)
        return -1;

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

/// <summary>
 

/// 設定系統音量
/// </summary>
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>
/// 設定系統靜音
/// </summary>
/// <param name="isMuted"></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);
}
}

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

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

    return masterVol;
}
finally
{
    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("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("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