[RESOLVED] Detecting Drive Letter of USB Drive

[chris128]

OK I got it working
Just in case anyone else ever wants to do a similar thing, here's my code:

EDIT: See updated code in post #13 for a better version

Imports System.Runtime.InteropServices
Public Class Form1
 
    Private Const WM_DEVICECHANGE As Integer = &H219
    Private Const DBT_DEVICEARRIVAL As Integer = &H8000
    Private Const DBT_DEVTYP_VOLUME As Integer = &H2
 
    'Device information structure
    Public Structure DEV_BROADCAST_HDR
        Public dbch_size As Int32
        Public dbch_devicetype As Int32
        Public dbch_reserved As Int32
    End Structure
 
    'Volume information Structure
    Private Structure DEV_BROADCAST_VOLUME
        Public dbcv_size As Int32
        Public dbcv_devicetype As Int32
        Public dbcv_reserved As Int32
        Public dbcv_unitmask As Int32
        Public dbcv_flags As Int16
    End Structure
 
    '<<<< Function that gets the drive letter from the unit mask >>>>
    Private Function GetDriveLetterFromMask(ByRef Unit As Int32)
        Dim i As Integer
        For i = 0 To 25
            If Unit And i Then Exit For
            Unit = Unit >> 1
        Next
        Return Chr(i + 1 + Asc("A"))
    End Function
 
    'Override message processing to check for the DEVICECHANGE message
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        If m.Msg = WM_DEVICECHANGE Then
            If m.WParam = DBT_DEVICEARRIVAL Then
                Dim DeviceInfo As DEV_BROADCAST_HDR
                DeviceInfo = Marshal.PtrToStructure(m.LParam, GetType(DEV_BROADCAST_HDR))
                If DeviceInfo.dbch_devicetype = DBT_DEVTYP_VOLUME Then
                    Dim Volume As DEV_BROADCAST_VOLUME
                    Volume = Marshal.PtrToStructure(m.LParam, GetType(DEV_BROADCAST_VOLUME))
                    Dim DriveLetter As String = (GetDriveLetterFromMask(Volume.dbcv_unitmask) & ":\")
                    Dim FileList() As String = IO.Directory.GetFiles(DriveLetter, "test.txt")
                    If FileList.Count > 0 Then
                        MessageBox.Show("Found Config File")
                        '<<<< The test file has been found >>>>
                        Else
                        MessageBox.Show("Could not find config file")
                        '<<<< Test file has not been found >>>>
                    End If
                End If
            End If
        End If
        MyBase.WndProc(m)
    End Sub
 
    
End Class