How To Implement IObjectSafety in Visual Basic Controls

SUMMARY

This article describes how to implement the IObjectSafety interface in Visual Basic controls to mark the controls safe for scripting and initialization. By default, Visual Basic controls use component category entries in the registry to mark the control safe for scripting and initialization. Implementing the IObjectSafety interface is the preferred method. This article contains all the code that is required to implement this interface in Visual Basic controls.

Please keep in mind that a control should only be marked as safe if it is, in fact, safe. This article does not describe the details of marking controls as safe for scripting and initialization; it simply demonstrates how to do it in code. Please refer to the Internet Client Software Development Kit (SDK) documentation for a detailed description of this. See "Safe Initialization and Scripting for ActiveX Controls" under the Component Development section.

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MORE INFORMATION

WARNING: One or more of the following functions are discussed in this article: VarPtr, VarPtrArray, VarPtrStringArray, StrPtr, and 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. For additional information about these functions, click the article number below to view the article in the Microsoft Knowledge Base:

199824 (http://support.microsoft.com/kb/199824/EN-US/) How To Get the Address of Variables in Visual Basic

The following steps illustrate how to create a simple Visual Basic control and mark it safe for scripting and initialization.

1.	Create a new folder where you can save all files that you create in this example.
2.	Get the OLE Automation Type Library Generator from the Visual Basic 6.0 CD-ROM. To do this, copy all four files from the \Common\Tools\VB\Unsupprt\Typlib\ folder to your project folder. Note: Copy all the files from \VB5.0\Tools\Unsupprt\Typlib\ folder in VIsual Basic 5.0.
3.	Copy the following text into Notepad, and save the file in the project folder as Objsafe.odl: [ uuid(C67830E0-D11D-11cf-BD80-00AA00575603), helpstring("VB IObjectSafety Interface"), version(1.0) ] library IObjectSafetyTLB { importlib("stdole2.tlb"); [ uuid(CB5BDC81-93C1-11cf-8F20-00805F2CD064), helpstring("IObjectSafety Interface"), odl ] interface IObjectSafety:IUnknown { [helpstring("GetInterfaceSafetyOptions")] HRESULT GetInterfaceSafetyOptions( [in] long riid, [in] long *pdwSupportedOptions, [in] long *pdwEnabledOptions); [helpstring("SetInterfaceSafetyOptions")] HRESULT SetInterfaceSafetyOptions( [in] long riid, [in] long dwOptionsSetMask, [in] long dwEnabledOptions); } }
4.	At a command prompt, use the CD <path> command to move to the project folder, and type the following command to generate a .tlb file: MKTYPLIB objsafe.odl /tlb objsafe.tlb
5.	From Visual Basic, create an ActiveX Control project. In the Properties list, change the name of the project to IObjSafety and the name of the control to DemoCtl. Put a CommandButton named cmdTest on the control. In the Click event handler of the cmdTest, put a MsgBox "Test" statement.
6.	On the Project menu, click References, browse to and add Objsafe.tlb, which you created earlier.
7.	Add a new module to your project with the following code, and name the module basSafeCtl: Option Explicit Public Const IID_IDispatch = "{00020400-0000-0000-C000-000000000046}" Public Const IID_IPersistStorage = _ "{0000010A-0000-0000-C000-000000000046}" Public Const IID_IPersistStream = _ "{00000109-0000-0000-C000-000000000046}" Public Const IID_IPersistPropertyBag = _ "{37D84F60-42CB-11CE-8135-00AA004BB851}" Public Const INTERFACESAFE_FOR_UNTRUSTED_CALLER = &H1 Public Const INTERFACESAFE_FOR_UNTRUSTED_DATA = &H2 Public Const E_NOINTERFACE = &H80004002 Public Const E_FAIL = &H80004005 Public Const MAX_GUIDLEN = 40 Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _ (pDest As Any, pSource As Any, ByVal ByteLen As Long) Public Declare Function StringFromGUID2 Lib "ole32.dll" (rguid As _ Any, ByVal lpstrClsId As Long, ByVal cbMax As Integer) As Long Public Type udtGUID Data1 As Long Data2 As Integer Data3 As Integer Data4(7) As Byte End Type Public m_fSafeForScripting As Boolean Public m_fSafeForInitializing As Boolean Sub Main() m_fSafeForScripting = True m_fSafeForInitializing = True End Sub
8.	From Project Properties, change the Startup Object to Sub Main to execute the Sub Main above. Use the m_fSafeForScripting and m_fSafeForInitializing variables to specify the values of safe for the scripting and/or initialization variables.
9.	Open the code window of your control. Add the following line of code to the Declaration section (right after Option Explicit or as the first): Implements IObjectSafety
10.	Copy the following two procedures to your controls code: Private Sub IObjectSafety_GetInterfaceSafetyOptions(ByVal riid As _ Long, pdwSupportedOptions As Long, pdwEnabledOptions As Long) Dim Rc As Long Dim rClsId As udtGUID Dim IID As String Dim bIID() As Byte pdwSupportedOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER Or _ INTERFACESAFE_FOR_UNTRUSTED_DATA If (riid <> 0) Then CopyMemory rClsId, ByVal riid, Len(rClsId) bIID = String$(MAX_GUIDLEN, 0) Rc = StringFromGUID2(rClsId, VarPtr(bIID(0)), MAX_GUIDLEN) Rc = InStr(1, bIID, vbNullChar) - 1 IID = Left$(UCase(bIID), Rc) Select Case IID Case IID_IDispatch pdwEnabledOptions = IIf(m_fSafeForScripting, _ INTERFACESAFE_FOR_UNTRUSTED_CALLER, 0) Exit Sub Case IID_IPersistStorage, IID_IPersistStream, _ IID_IPersistPropertyBag pdwEnabledOptions = IIf(m_fSafeForInitializing, _ INTERFACESAFE_FOR_UNTRUSTED_DATA, 0) Exit Sub Case Else Err.Raise E_NOINTERFACE Exit Sub End Select End If End Sub Private Sub IObjectSafety_SetInterfaceSafetyOptions(ByVal riid As _ Long, ByVal dwOptionsSetMask As Long, ByVal dwEnabledOptions As Long) Dim Rc As Long Dim rClsId As udtGUID Dim IID As String Dim bIID() As Byte If (riid <> 0) Then CopyMemory rClsId, ByVal riid, Len(rClsId) bIID = String$(MAX_GUIDLEN, 0) Rc = StringFromGUID2(rClsId, VarPtr(bIID(0)), MAX_GUIDLEN) Rc = InStr(1, bIID, vbNullChar) - 1 IID = Left$(UCase(bIID), Rc) Select Case IID Case IID_IDispatch If ((dwEnabledOptions And dwOptionsSetMask) <> _ INTERFACESAFE_FOR_UNTRUSTED_CALLER) Then Err.Raise E_FAIL Exit Sub Else If Not m_fSafeForScripting Then Err.Raise E_FAIL End If Exit Sub End If Case IID_IPersistStorage, IID_IPersistStream, _ IID_IPersistPropertyBag If ((dwEnabledOptions And dwOptionsSetMask) <> _ INTERFACESAFE_FOR_UNTRUSTED_DATA) Then Err.Raise E_FAIL Exit Sub Else If Not m_fSafeForInitializing Then Err.Raise E_FAIL End If Exit Sub End If Case Else Err.Raise E_NOINTERFACE Exit Sub End Select End If End Sub
11.	On the File menu, save your project and files. Make an OCX file from your project. Your control now implements the IObjectSafety interface. To test it, insert the control in an .htm file.

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REFERENCES

MkTypLib.exe is an old tool that previously shipped with the Platform Software Development Kit (SDK) that comes with Microsoft Visual Studio 6.0. For information on how to install the Platform SDK that comes with Visual Studio 6.0, see the following Microsoft Web site:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sdkintro/sdkintro/installing_the_platform_sdk_with_visual_studio.asp (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sdkintro/sdkintro/installing_the_platform_sdk_with_visual_studio.asp)

The current Platform SDK does not come with the MkTypLib.exe tool. For information about what Microsoft products ship the Type Library Compiler (MkTypLib.exe), see the following Microsoft DLL Help database and search on the file name MkTypLib.exe

http://support.microsoft.com/dllhelp (http://support.microsoft.com/?scid=http%3a%2f%2fsupport.microsoft.com%2fservicedesks%2ffileversion%2fdllinfo.asp)

For information about how to invoke MkTypLib, see the following Microsoft Web site:

http://www.microsoft.com/msj/0297/visualprog/visualprog0297.aspx (http://www.microsoft.com/msj/0297/visualprog/visualprog0297.aspx)

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

161873 (http://support.microsoft.com/kb/161873/EN-US/) How To Mark MFC Controls Safe for Scripting/Initialization

143258 (http://support.microsoft.com/kb/143258/EN-US/) How To Create Constants and DLL Declarations in a Type Library

131105 (http://support.microsoft.com/kb/131105/EN-US/) SAMPLE: TYPEBLD: How to Use ICreateTypeLib and ICreateTypeInfo

For more information about the IObjectSafety interface, see the following Microsoft Web site:

http://msdn.microsoft.com/workshop/components/com/reference/ifaces/iobjectsafety/iobjectsafety.asp (http://msdn.microsoft.com/workshop/components/com/reference/ifaces/iobjectsafety/iobjectsafety.asp)

For more information about safe initialization and scripting for ActiveX controls, see the following Microsoft Web site:

http://msdn.microsoft.com/workshop/components/activex/safety.asp (http://msdn.microsoft.com/workshop/components/activex/safety.asp)

For more information about developing Web-based solutions for Microsoft Internet Explorer, visit the following Microsoft Web sites:

http://msdn.microsoft.com/ie/ (http://msdn.microsoft.com/ie/)

http://support.microsoft.com/iep (http://support.microsoft.com/iep)

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