Vb6 Opening a custom file with my program in a text box

Question

Help I am making a word processor and have a custom file extension to save it with but when I save that file and use open with select my program's exe then open it, the program opens with blank text how would I get it to open my text from double click in windows explorer

Answer 1

Inside your code use the following (no way to make it pretty but it works fine, copy and paste)

Private Declare Function RegCreateKey Lib "advapi32.dll" Alias "RegCreateKeyA" (ByVal hKey As Long, ByVal lpSubKey As String, phkResult As Long) As Long
Private Declare Function RegSetValue Lib "advapi32.dll" Alias "RegSetValueA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal dwType As Long, ByVal lpData As String, ByVal cbData As Long) As Long
Private Declare Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) As Long
Private Declare Function RegOpenKey Lib "advapi32.dll" Alias "RegOpenKeyExA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, ByVal samDesired As Long, phkResult As Long) As Long
Private Declare Function RegQueryValue Lib "advapi32.dll" Alias "RegQueryValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal lpReserved As Long, lpType As Long, ByVal lpData As String, lpcbData As Long) As Long
Private Declare Function RegDeleteKey Lib "advapi32.dll" Alias "RegDeleteKeyA" (ByVal hKey As Long, ByVal lpSubKey As String) As Long

Private Const ERROR_SUCCESS = 0&
Private Const ERROR_BADDB = 1&
Private Const ERROR_BADKEY = 2&
Private Const ERROR_CANTOPEN = 3&
Private Const ERROR_CANTREAD = 4&
Private Const ERROR_CANTWRITE = 5&
Private Const ERROR_OUTOFMEMORY = 6&
Private Const ERROR_INVALID_PARAMETER = 7&
Private Const ERROR_ACCESS_DENIED = 8&

Private Const KEY_QUERY_VALUE = &H1&
Private Const KEY_CREATE_SUB_KEY = &H4&
Private Const KEY_ENUMERATE_SUB_KEYS = &H8&
Private Const KEY_NOTIFY = &H10&
Private Const KEY_SET_VALUE = &H2&
Private Const MAX_PATH = 260&
Private Const REG_DWORD As Long = 4
Private Const REG_SZ = 1
Private Const READ_CONTROL = &H20000
Private Const STANDARD_RIGHTS_READ = READ_CONTROL
Private Const STANDARD_RIGHTS_WRITE = READ_CONTROL

Private Const KEY_READ = STANDARD_RIGHTS_READ Or KEY_QUERY_VALUE Or KEY_ENUMERATE_SUB_KEYS Or KEY_NOTIFY
Private Const KEY_WRITE = STANDARD_RIGHTS_WRITE Or KEY_SET_VALUE Or KEY_CREATE_SUB_KEY

Public Const HKEY_CLASSES_ROOT = &H80000000
Public Const HKEY_CURRENT_USER = &H80000001
Public Const HKEY_LOCAL_MACHINE = &H80000002
Public Const HKEY_USERS = &H80000003

Public Sub MakeFileAssociation(Extension As String, PathToApplication As String, ApplicationName As String, Description As String, Optional FullIconPath As String)
    Dim ret&

    If Left(PathToApplication, 1) <> "\" Then PathToApplication = PathToApplication & "\"
    'Create a Root entry called .XXX associated with application name
    sKeyName = "." & Extension
    sKeyValue = ApplicationName
    ret& = WriteKey(HKEY_CLASSES_ROOT, sKeyName, "", sKeyValue)
    'Set application key and file description
    sKeyName = ApplicationName
    sKeyValue = Description
    ret& = WriteKey(HKEY_CLASSES_ROOT, sKeyName, "", sKeyValue)
    'This sets the default icon for XXX_auto_file
    If FullIconPath <> "" Then
    sKeyName = ApplicationName & "\DefaultIcon"
    sKeyValue = FullIconPath & ",0"
    ret& = WriteKey(HKEY_CLASSES_ROOT, sKeyName, "", sKeyValue)
    End If
    'This sets the command line for XXX_auto_file
    sKeyName = ApplicationName & "\shell\open\command"
    sKeyValue = Chr(34) & PathToApplication & ApplicationName & ".exe" & Chr(34) & " %1"
    ret& = WriteKey(HKEY_CLASSES_ROOT, sKeyName, "", sKeyValue)
End Sub

Public Sub DeleteFileAssociation(Extension As String)
    Dim Application As String
    Dim ret&
    'check if filetype is registred
    Application = ReadKey(HKEY_CLASSES_ROOT, "." & Extension, "", "")
    If Application <> "" Then
    'delete file extension
    ret& = DeleteKey(HKEY_CLASSES_ROOT, "." & Extension)
    'delete command lines
    ret& = DeleteKey(HKEY_CLASSES_ROOT, Application)
    End If
End Sub

Public Function CheckFileAssociation(ByVal Extension As String) As String
    Extension = "." & Extension
    'read in the program name associated with this filetype
    CheckFileAssociation = ReadKey(HKEY_CLASSES_ROOT, Extension, "", "")
End Function

Public Function ReadKey(ByVal KeyName As String, ByVal SubKeyName As String, ByVal ValueName As String, ByVal DefaultValue As String) As String
    Dim sBuffer As String
    Dim lBufferSize As Long
    Dim ret&
    sBuffer = Space(255)
    lBufferSize = Len(sBuffer)
    ret& = RegOpenKey(KeyName, SubKeyName, 0, KEY_READ, lphKey&)
    If ret& = ERROR_SUCCESS Then
    ret& = RegQueryValue(lphKey&, ValueName, 0, REG_SZ, sBuffer, lBufferSize)
    ret& = RegCloseKey(lphKey&)
    Else
    ret& = RegCloseKey(lphKey&)
    End If
    sBuffer = Trim(sBuffer)
    If sBuffer <> "" Then
    sBuffer = Left(sBuffer, Len(sBuffer) - 1)
    Else
    sBuffer = DefaultValue
    End If
    ReadKey = sBuffer
End Function

Public Function WriteKey(ByVal KeyName As String, ByVal SubKeyName As String, ByVal ValueName As String, ByVal KeyValue As String) As Long
    Dim ret&
    ret& = RegCreateKey&(KeyName, SubKeyName, lphKey&)
    If ret& = ERROR_SUCCESS Then
    ret& = RegSetValue&(lphKey&, ValueName, REG_SZ, KeyValue, 0&)
    Else
    ret& = RegCloseKey(lphKey&)
    End If
    WriteKey = ret&
End Function

Public Function DeleteKey(ByVal KeyName As String, ByVal SubKeyName As String) As Long
    Dim ret&
    ret& = RegOpenKey(KeyName, SubKeyName, 0, KEY_WRITE, lphKey&)
    If ret& = ERROR_SUCCESS Then
    ret& = RegDeleteKey(lphKey&, "") 'delete the key
    ret& = RegCloseKey(lphKey&)
    End If
    DeleteKey = ret&
End Function

Then you can call them and provide the parameter and it will create it for you, delete it and check it. As for handing it via your application when you open the file using the extension, you need to make sure you have a command line parser and feed it with a %1 and use that file name to open the document within your program. That's it.

You can create a main() and set your program startup to use that instead of the usual form1 and inside that put:

Public Sub main()
    'Store command line arguments in this array
    Dim sArgs() As String

    Dim iLoop As Integer
    'Assuming that the arguments passed from 
    'command line will have space in between, 
    'you can also use comma or other things...
    sArgs = Split(Command$, " ")
    For iLoop = 0 To UBound(sArgs)
        'this will print the command line
        'arguments that are passed from the command line
        Debug.Print sArgs(iLoop)
    Next
End Sub

Depending on what arguments you are passing to the command of your program, you would replace the debug line with the path to the file you just opened with your program and do what you do with it in your application.