Imports NAudio.Wave
Public Class Form1
    Private wave As NAudio.Wave.WaveFileReader = Nothing
    Private output As NAudio.Wave.AsioOut = Nothing

    Public Sub New()
        InitializeComponent()
        InitialiseAsioControls()
    End Sub

    Public ReadOnly Property SelectedDeviceName() As String
        Get
            Return CStr(comboBoxAsioDriver.SelectedItem)
        End Get
    End Property

    Private Sub InitialiseAsioControls()
        ' Just fill the comboBox AsioDriver with available driver names
        Dim asioDriverNames = AsioOut.GetDriverNames()
        For Each driverName As String In asioDriverNames
            comboBoxAsioDriver.Items.Add(driverName)
        Next driverName
        comboBoxAsioDriver.SelectedIndex = 0
    End Sub

    Private Sub btnOpen_Click(sender As System.Object, e As System.EventArgs) Handles btnOpen.Click
        Dim wavFile As String
        OpenWavFile.InitialDirectory = ""
        wavFile = OpenWavFile.ShowDialog()
        wavFile = OpenWavFile.FileName
        Label1.Text = wavFile
    End Sub

    Private Sub btnPlay_Click(sender As System.Object, e As System.EventArgs) Handles btnPlay.Click
        If Label1.Text = Nothing Then
            Dim wavFile As String
            OpenWavFile.InitialDirectory = ""
            wavFile = OpenWavFile.ShowDialog()
            wavFile = OpenWavFile.FileName
            Label1.Text = wavFile
        Else
            wave = New NAudio.Wave.WaveFileReader(Label1.Text)
            output = New AsioOut(comboBoxAsioDriver.Text)
            output.Init(New NAudio.Wave.WaveChannel32(wave))
            output.Play()
            btnPlay.Enabled = False
        End If
    End Sub

    Private Sub DisposeWave()
        If output IsNot Nothing Then
            If output.PlaybackState = NAudio.Wave.PlaybackState.Playing Then
                output.Stop()
            End If
            output.Dispose()
            output = Nothing
        End If
        If wave IsNot Nothing Then
            wave.Dispose()
            wave = Nothing
        End If
    End Sub

    Private Sub btnStop_Click(sender As System.Object, e As System.EventArgs) Handles btnStop.Click
        DisposeWave()
        btnPlay.Enabled = True
    End Sub
End Class

    Private Sub DisposeWave()
        If output IsNot Nothing Then
            If output.PlaybackState = NAudio.Wave.PlaybackState.Playing Then
                output.Stop()
            End If
            output.Dispose()
            output = Nothing
        End If
        If wave IsNot Nothing Then
            wave.Dispose()
            wave = Nothing
        End If

    End Sub

    Private Sub btnStop_Click(sender As System.Object, e As System.EventArgs) Handles btnStop.Click
        output.Stop()
        DisposeWave()
        btnPlay.Enabled = True
    End Sub

Private WithEvents output As NAudio.Wave.AsioOut = Nothing
Private mainOutputStream As WaveChannel32
... 
mainOutputStream = New WaveChannel32(wave) ' tie the file reader to the output stream 
mainOutputStream.PadWithZeroes = False ' need this to detect eof
output.Init(mainOutputStream) ' tie output stream to output device
...

Private Sub PlaybackStopped(sender As Object, e As System.EventArgs) Handles output.PlaybackStopped
        ' dispose
End Sub

Imports NAudio.Wave

Public Class Form1
    Private reader As WaveFileReader
    Private asioOut As AsioOut
    Public Sub New()
        InitializeComponent()
        AddHandler Disposed, AddressOf AsioDirectPanel_Disposed
        For Each device In AsioOut.GetDriverNames()
            Me.comboBoxAsioDevice.Items.Add(device)
        Next device
        If Me.comboBoxAsioDevice.Items.Count > 0 Then
            Me.comboBoxAsioDevice.SelectedIndex = 0
        End If
    End Sub

    Private Sub AsioDirectPanel_Disposed(ByVal sender As Object, ByVal e As EventArgs)
        Cleanup()
    End Sub

    Private Sub Cleanup()
        If Me.asioOut IsNot Nothing Then
            Me.asioOut.Dispose()
            Me.asioOut = Nothing
        End If
        If Me.reader IsNot Nothing Then
            Me.reader.Dispose()
            Me.reader = Nothing
        End If
    End Sub

    Private Sub buttonSelectFile_Click_1(sender As System.Object, e As System.EventArgs) Handles buttonSelectFile.Click
        Cleanup()
        Dim ofd As New OpenFileDialog()
        ofd.Filter = "WAV files|*.wav"
        If ofd.ShowDialog() = DialogResult.OK Then
            Me.reader = New WaveFileReader(ofd.FileName)
        End If
    End Sub

    Private Sub buttonPlay_Click(ByVal sender As Object, ByVal args As EventArgs) Handles buttonPlay.Click
        Try
            Play()
        Catch e As Exception
            MessageBox.Show(e.Message)
        End Try
    End Sub

    Private Function GetUserSpecifiedChannelOffset() As Integer
        Dim channelOffset As Integer = 0
        Integer.TryParse(textBoxChannelOffset.Text, channelOffset)
        Return channelOffset
    End Function

    Private Sub Play()
        ' allow change device
        If Me.asioOut IsNot Nothing AndAlso (Me.asioOut.DriverName <> comboBoxAsioDevice.Text OrElse Me.asioOut.ChannelOffset <> GetUserSpecifiedChannelOffset()) Then
            Me.asioOut.Dispose()
            Me.asioOut = Nothing
        End If

        ' create device if necessary
        If Me.asioOut Is Nothing Then
            Me.asioOut = New AsioOut(comboBoxAsioDevice.Text)
            Me.asioOut.ChannelOffset = GetUserSpecifiedChannelOffset()
            Me.asioOut.Init(Me.reader)
        End If

        Me.reader.Position = 0
        Me.asioOut.Play()
        Me.Timer1.Enabled = True
        SetButtonStates()
    End Sub

    Private Sub SetButtonStates()
        buttonPlay.Enabled = asioOut IsNot Nothing AndAlso asioOut.PlaybackState <> PlaybackState.Playing
        buttonStop.Enabled = asioOut IsNot Nothing AndAlso asioOut.PlaybackState = PlaybackState.Playing
    End Sub

    Private Sub buttonStop_Click(ByVal sender As Object, ByVal e As EventArgs) Handles buttonStop.Click
        Me.Stop()
    End Sub

    Private Sub [Stop]()
        Me.asioOut.Stop()
        Me.Timer1.Enabled = False
        SetButtonStates()
    End Sub

    Private Sub timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick
        If asioOut IsNot Nothing AndAlso asioOut.PlaybackState = PlaybackState.Playing AndAlso reader.Position >= reader.Length Then
            Me.Stop()
        End If
    End Sub
End Class