Imports System.Runtime.InteropServices

Public Class Form1
Inherits System.Windows.Forms.Form

Private Declare Auto Function SHGetFileInfo Lib "shell32.dll" ( _
ByVal pszPath As String, _
ByVal dwFileAttributes As Integer, _
ByRef psfi As SHFILEINFO, _
ByVal cbFileInfo As Integer, _
ByVal uFlags As Integer _
) As IntPtr

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> _
Private Structure SHFILEINFO
Public hIcon As Int32
Public iIcon As Int32
Public dwAttributes As Int32
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=260)> _
Public szDisplayName As String
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=80)> _
Public szTypeName As String
End Structure

Private Const SHGFI_TYPENAME As Int32 = &H400

#Region " Vom Windows Form Designer generierter Code "
[...]
#End Region

Private Sub Form1_Load( _
ByVal sender As System.Object, _
ByVal e As System.EventArgs _
) Handles MyBase.Load
Dim x As SHFILEINFO
SHGetFileInfo("C:\test_tl\ausarb.tex", 0, x, Len(x), SHGFI_TYPENAME)
MsgBox(x.szTypeName)
End Sub
End Class