ID: Q180217
DCOM allows clients to create and use OLE servers located on other computers. One means for controlling the server location is through the settings in the client computer's registry. These settings can be configured using DCOM Config (Dcomcnfg.exe), a Microsoft Transaction Server client installation executable, or other setup programs.
However, a second and more flexible means of controlling server location is to use the new CoCreateInstanceEx function provided by DCOM. The code provided in the "More Information" section of this article wraps the CoCreateInstanceEx function in CreateObjectEx (a Visual Basic function).
WARNING: ANY USE BY YOU OF THE CODE PROVIDED IN THIS ARTICLE IS AT YOUR OWN RISK. Microsoft provides this code "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.
To use CreateObjectEx, add a module to your Visual Basic project and insert the following code into the module.
You may now call CreateObjectEx as follows:
Dim obj As Object
Set obj = CreateObjectEx("MyServer.MyClass", "ServerMachineName")
Several formats are available for the arguments, and these are described in detail in the following section of this article.
A third argument is available to control the binding type. If you are using early binding, you may wish to use this syntax:
Dim obj as MyServer.MyClass
Set obj = CreateObjectEx("MyServer.MyClass", "ServerMachineName", _
EARLY_BINDING)
Option Explicit
Private Type GUID
Data1 As Long
Data2 As Integer
Data3 As Integer
Data4(7) As Byte
End Type
Private Type COSERVERINFO
dwReserved1 As Long 'DWORD
pwszName As Long 'LPWSTR
pAuthInfo As Long 'COAUTHINFO *
dwReserved2 As Long 'DWORD
End Type
Type MULTI_QI
pIID As Long 'const IID*
pItf As Object 'Interface *
hr As Long 'HRESULT
End Type
Public Enum BindingType
EARLY_BINDING = 0
LATE_BINDING = 1
End Enum
Public Enum CLSCTX
CLSCTX_INPROC_SERVER = 1
CLSCTX_INPROC_HANDLER = 2
CLSCTX_LOCAL_SERVER = 4
CLSCTX_REMOTE_SERVER = 16
CLSCTX_SERVER = CLSCTX_INPROC_SERVER + CLSCTX_LOCAL_SERVER _
+ CLSCTX_REMOTE_SERVER
CLSCTX_ALL = CLSCTX_INPROC_SERVER + CLSCTX_INPROC_HANDLER _
+ CLSCTX_LOCAL_SERVER + CLSCTX_REMOTE_SERVER
End Enum
Private Const IID_IUnknown As String = _
"{00000000-0000-0000-C000-000000000046}"
Private Const IID_IDispatch As String = _
"{00020400-0000-0000-C000-000000000046}"
Private Declare Function CLSIDFromString Lib "OLE32" _
(ByVal lpszCLSID As Long, pclsid As GUID) As Long
Private Declare Function CLSIDFromProgID Lib "OLE32" _
(ByVal lpszProgID As Long, pclsid As GUID) As Long
Private Declare Function CoCreateInstanceEx Lib "OLE32" _
(rclsid As GUID, ByVal pUnkOuter As Long, _
ByVal dwClsContext As Long, pServerInfo As COSERVERINFO, _
ByVal cmq As Long, rgmqResults As MULTI_QI) As Long
' Public Function CreateObjectEx
' Creates an Instance of an OLE Server on a specified computer.
'
' Arguments:
'
' The Class argument specifies the OLE Server.
' There are two formats for the Class argument:
' 1. PROGID: "Excel.Application"
' 2. CLSID: "{00000010-0000-0010-8000-00AA006D2EA4}"
' If a ProgID is used, the client's registry is used to get the CLSID.
'
' The Server argument specifies the server computer.
' There are two formats for the Server argument:
' 1. UNC ("\\ServerName" or "ServerName")
' 2. DNS ("server.sub.com" or "135.5.33.19")
' The Server argument is optional. If it is not supplied,
' the ole server is created on the client computer.
'
' The Binding argument specifies the type of binding used by client.
' There are two values: EARLY_BINDING and LATE_BINDING.
'
' If the client uses late binding (e.g. dim obj as Object),
' it must use the LATE_BINDING value or omit the Binding argument.
' If the client uses early binding (e.g. dim obj as MySvr.MyClass),
' it may use either LATE_BINDING or EARLY_BINDING.
' Some OLE servers will work only with LATE_BINDING, others
' only with EARLY_BINDING, and others with either binding type.
' OLE servers written in Visual Basic 5.0 support both binding types.
'
Public Function CreateObjectEx(ByVal Class As String, _
Optional ByVal Server As String = "", _
Optional Binding As BindingType = LATE_BINDING) As Object
Dim rclsid As GUID
Dim riid As GUID
Dim hr As Long
Dim ServerInfo As COSERVERINFO
Dim mqi As MULTI_QI
Dim Context As Long
' Convert IID string to binary IID
If Binding = EARLY_BINDING Then
hr = CLSIDFromString(StrPtr(IID_IUnknown), riid)
Else
hr = CLSIDFromString(StrPtr(IID_IDispatch), riid)
End If
If hr <> 0 Then Err.Raise hr
'Setup the MULTI_QI structure.
mqi.pIID = VarPtr(riid)
'Convert provided CLSID or ProgID string into a binary CLSID
If ((Left(Class, 1) = "{") And (Right(Class, 1) = "}") _
And (Len(Class) = 38)) Then
hr = CLSIDFromString(StrPtr(Class), rclsid)
Else
hr = CLSIDFromProgID(StrPtr(Class), rclsid)
End If
If hr <> 0 Then Err.Raise hr
'Decide on the appropriate context value.
If Server = "" Then
Context = CLSCTX_SERVER
Else
Context = CLSCTX_REMOTE_SERVER
End If
'Setup the COSERVERINFO structure.
ServerInfo.pwszName = StrPtr(Server)
' Create an instance of the object
hr = CoCreateInstanceEx(rclsid, CLng(0), Context, _
ServerInfo, CLng(1), mqi)
If hr <> 0 Then Err.Raise hr
Set CreateObjectEx = mqi.pItf
End Function
For additional information about Transaction Server, please see the following Microsoft Web sites:
http://support.microsoft.com/support/default.asp
http://www.microsoft.com/transaction/
Keywords : TSrvDeploy
Version : WINDOWS:5.0; WINNT:1.0,2.0
Platform : WINDOWS winnt
Issue type : kbhowtoLast Reviewed: February 27, 1998