How To Call CLSID And ProgID Related COM APIs in Visual Basic (183544)

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WARNING: One or more of the following functions are discussed in this article; VarPtr, VarPtrArray, VarPtrStringArray, StrPtr, ObjPtr. These functions are not supported by Microsoft Technical Support. They are not documented in the Visual Basic documentation and are provided in this Knowledge Base article "as is." Microsoft does not guarantee that they will be available in future releases of Visual Basic.

1. Create a new ActiveX DLL project (Project1) in Visual Basic (Class1 is created by default).
2. Compile the default project. Now, you have a test component: Project1.dll, which contains a COM class (Project1.Class1)
3. Create a new Standard EXE project (Project1) in Visual Basic. Form1 is created by default.
4. Add three TextBoxes, one Command button, and one ListBox to Form1.
5. Add the following code to Form1's code module:

         ' ========== CODE FOR FORM1 ==============
         Option Explicit
   
         'CLSID/GUID structure
         '====================
   
         Private Type GUID
             Data1 As Long
             Data2 As Integer
             Data3 As Integer
             Data4(7) As Byte
         End Type
   
         'API Declarations:
         '=================
   
         Private Declare Function CLSIDFromProgID _
            Lib "ole32.dll" (ByVal lpszProgID As Long, _
            pCLSID As GUID) As Long
   
         Private Declare Function ProgIDFromCLSID _
            Lib "ole32.dll" (pCLSID As GUID, lpszProgID As Long) As Long
   
         Private Declare Function StringFromCLSID _
            Lib "ole32.dll" (pCLSID As GUID, lpszProgID As Long) As Long
   
         Private Declare Function CLSIDFromString _
            Lib "ole32.dll" (ByVal lpszProgID As Long, _
            pCLSID As GUID) As Long
   
         Private Declare Sub CopyMemory Lib "kernel32" Alias _
            "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal ByteLen As Long)
   
         Private Sub Command1_Click()
            Dim strProgID As String * 255
            Dim pProgID As Long
            Dim udtCLSID As GUID
            Dim strCLSID As String * 255
            Dim pCLSID As Long
            Dim lngRet As Long
            Dim strTemp As String
            Dim i As Integer
   
            'Take a ProgID.
            strTemp = Text1.Text
   
            'Get CLSID.
            lngRet = CLSIDFromProgID(StrPtr(strTemp), udtCLSID)
   
            'Display CLSID elements.
            With List1
               .AddItem Hex(udtCLSID.Data1)
               .AddItem Hex(udtCLSID.Data2)
               .AddItem Hex(udtCLSID.Data3)
               For i = 0 To 7
                  .AddItem Hex(udtCLSID.Data4(i))
               Next
            End With
   
            'Convert CLSID to a string and get the pointer back.
            lngRet = StringFromCLSID(udtCLSID, pCLSID)
   
            'Get the CLSID string and display it.
            StringFromPointer pCLSID, strCLSID
            Text2.Text = strCLSID
   
            'Reinitialize the CLSID.
            With udtCLSID
               .Data1 = 0
               .Data2 = 0
               .Data3 = 0
               For i = 0 To 7
                  .Data4(i) = 0
               Next
            End With
   
            'Convert the string back to CLSID.
            strTemp = Text2.Text
            lngRet = CLSIDFromString(StrPtr(strTemp), udtCLSID)
   
            'Get a pointer to ProgID string. This is a Unicode string.
            lngRet = ProgIDFromCLSID(udtCLSID, pProgID)
   
            'Get the ProgID and display it.
            StringFromPointer pProgID, strProgID
            Text3.Text = strProgID
   
         End Sub
   
         'This function takes a pointer to a Unicode string, a string buffer
         'and place the bytes in the Visual Basic string buffer.
   
         Private Sub StringFromPointer(pOLESTR As Long, strOut As String)
            Dim ByteArray(255) As Byte
            Dim intTemp As Integer
            Dim intCount As Integer
            Dim i As Integer
   
            intTemp = 1
   
            'Walk the string and retrieve the first byte of each WORD.
            While intTemp <> 0
               CopyMemory intTemp, ByVal pOLESTR + i, 2
               ByteArray(intCount) = intTemp
               intCount = intCount + 1
               i = i + 2
            Wend
   
            'Copy the byte array to our string.
            CopyMemory ByVal strOut, ByteArray(0), intCount
         End Sub
   
         Private Sub Form_Load()
            Text1.Text = "Project1.Class1"
         End Sub
   					

6. Run the project, and press Command1. The following appears: