VB Shell Programming

Property Sheet Handler Interface

Now that you know how a property sheet handler works, let’s discuss the interfaces involved in a little more detail.

IShellExtInit

The implementation of IShellExtInit is exactly the same as it was in Chapter 4. (For the details of the IShellExtInit interface, see Section 4.4 in Chapter 4.) Well, almost. The functionality provided by IShellExtInit—which is used to determine which files are selected in the Explorer—is generic enough to be wrapped in a class. All future extensions that must implement IShellExtInit in this book will use this class. The class is called clsDropFiles, and the complete class listing is shown in Example 6.1.

Example 6-1. clsDropFiles Class

Option Explicit Private m_nFiles As Long Private m_sDropFiles( ) As String Public Sub GetDropFiles(pDataObj As IDataObject, _ ByVal sExtension As String) Dim FmtEtc As FORMATETC Dim pMedium As STGMEDIUM Dim i As Long Dim lresult As Long Dim sTemp As String Dim lIndex As Long With FmtEtc .cfFormat = CF_HDROP .ptd = 0 .dwAspect = DVASPECT_CONTENT .lIndex = -1 .TYMED = TYMED_HGLOBAL End With pDataObj.GetData FmtEtc, pMedium m_nFiles = DragQueryFile(pMedium.pData, &HFFFFFFFF, _ vbNullString, 0) lIndex = 0 For i = 0 To m_nFiles - 1 sTemp = Space(255) lresult = DragQueryFile(pMedium.pData, i, sTemp, Len(sTemp)) If (lresult > 0) Then sTemp = Left$(sTemp, lresult) If LCase(Right(sTemp, 4)) = sExtension Then ReDim Preserve m_sDropFiles(lIndex + 1) m_sDropFiles(lIndex) = sTemp lIndex = lIndex ...