Logic Question

Question

Hello experts,
Need a how-to-do advise:
I use this to show my help file:

Help.ShowHelp(Me, "path\help.chm", "StartPage.htm")

I need to delete this file after my app's exit:
"path\help.chm"

The problem's that if the help file is being shown and the time of app's shut down, can't delete on startup form's Closed/Finalized events!
Help. does not have a method to close the shown help, also can't find it using process.kill before trying to delete on Closed/Finalized event!
* Since on each form's help_requested Help.ShowHelp is being called for the same file but with different pages I have to use it...
Any advise you might think of?
Thanks indeed.

Answer 1

You can use directly HtmlHelp API, which returns a window handle and has a command to close it
I tested with your code and it worked with my .chm

Global variables :

Public HelpFile As String = Path.GetTempPath() + "\Help.chm"  
Public hWndHelp As IntPtr = Nothing  

To open a .chm (I tested the topic with my .chm, to be changed...) :

hWndHelp = HtmlHelp(Me.Handle, HelpFile + "::/inet401/help/itt/CommCtls/Common/Common.htm#Using_Common_Control",  
            HH_DISPLAY_TOPIC, IntPtr.Zero)  

To close HTMLHelp window (before deleting the .chm)

 HtmlHelp(Me.Handle, Nothing, HH_CLOSE_ALL, IntPtr.Zero)  

Declarations :

<DllImport("Hhctrl.ocx", SetLastError:=True, CharSet:=CharSet.Unicode)>  
Public Shared Function HtmlHelp(hwndCaller As IntPtr, pszFile As String, uCommand As UInteger, dwData As IntPtr) As IntPtr  
End Function  

Public Const HH_DISPLAY_TOPIC = &H0  
Public Const HH_HELP_FINDER = &H0  ' WinHelp equivalent  
Public Const HH_DISPLAY_TOC = &H1  
Public Const HH_DISPLAY_INDEX = &H2  
Public Const HH_DISPLAY_SEARCH = &H3  
Public Const HH_SET_WIN_TYPE = &H4  
Public Const HH_GET_WIN_TYPE = &H5  
Public Const HH_GET_WIN_HANDLE = &H6  
Public Const HH_ENUM_INFO_TYPE = &H7  ' Get Info type name, call repeatedly to enumerate, -1 at end  
Public Const HH_SET_INFO_TYPE = &H8  ' Add Info type to filter.  
Public Const HH_SYNC = &H9  
Public Const HH_RESERVED1 = &HA  
Public Const HH_RESERVED2 = &HB  
Public Const HH_RESERVED3 = &HC  
Public Const HH_KEYWORD_LOOKUP = &HD  
Public Const HH_DISPLAY_TEXT_POPUP = &HE  ' display string resource id or text in a popup window  
Public Const HH_HELP_CONTEXT = &HF  ' display mapped numeric value in dwData  
Public Const HH_TP_HELP_CONTEXTMENU = &H10  ' text popup help, same as WinHelp HELP_CONTEXTMENU  
Public Const HH_TP_HELP_WM_HELP = &H11  ' text popup help, same as WinHelp HELP_WM_HELP  
Public Const HH_CLOSE_ALL = &H12  ' close all windows opened directly or indirectly by the caller  
Public Const HH_ALINK_LOOKUP = &H13  ' ALink version of HH_KEYWORD_LOOKUP  
Public Const HH_GET_LAST_ERROR = &H14  ' not currently implemented ' See HHERROR.h  
Public Const HH_ENUM_CATEGORY = &H15    ' Get category name, call repeatedly to enumerate, -1 at end  
Public Const HH_ENUM_CATEGORY_IT = &H16  ' Get category info type members, call repeatedly to enumerate, -1 at end  
Public Const HH_RESET_IT_FILTER = &H17  ' Clear the info type filter of all info types.  
Public Const HH_SET_INCLUSIVE_FILTER = &H18  ' set inclusive filtering method for untyped topics to be included in display  
Public Const HH_SET_EXCLUSIVE_FILTER = &H19  ' set exclusive filtering method for untyped topics to be excluded from display  
Public Const HH_INITIALIZE = &H1C  ' Initializes the help system.  
Public Const HH_UNINITIALIZE = &H1D  ' Uninitializes the help system.  
Public Const HH_SET_QUERYSERVICE = &H1E  ' Set the Host IQueryService interface  
Public Const HH_PRETRANSLATEMESSAGE = &HFD  ' Pumps messages. (NULL, NULL, MSG*).   
Public Const HH_SET_GLOBAL_PROPERTY = &HFC  ' Set a global property. (NULL, NULL, HH_GPROP)  
Public Const HH_SAFE_DISPLAY_TOPIC = &H20  ' private addition to the interface for InternetExplorer.  

Answer 2

The problem's that if the help file is being shown and the time of app's shut down, can't delete on startup form's Closed/Finalized events!

I cannot reproduce this (Windows 10 21H1)
If I open a .chm, I can delete it on closing even if it is opened

I tested with :

Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing  
    Dim sFile As String = "E:\temp\SHELLCC.CHM"  
    If (My.Computer.FileSystem.FileExists(sFile)) Then  
        My.Computer.FileSystem.DeleteFile(sFile)  
    End If  
End Sub