Generating OPC Automation IDL, TLB and header files from OPCDAAuto.dll

OPC Automation IDL, TLB and header files are not easy to find. You can obtain this files from OPC Foundation if you are a member or maybe from OPC application vendor.

The IDL file can be reverse engineered using OLE-Com Object Viewer. Once the IDL is generated TLB and other files can be generated from it as well. Below is a general direction how to do this.

Steps to reverse generate IDL, TLB and header files for OPCDAAuto.dll:

1. Download Windows 7 SDK. I am using GRMSDKX_EN_DVD.iso as the OS is Windows 7 64-bit.
2. Install the SDK.
3. Open CMD Shell (Start | All Programs | Microsoft Windows SDK v7.0 | CMD Shell)
4. Change directory to bin folder.
5. Run oleview.exe, this will open a 32-bit version of the application. Note that this is important as the OPCDAAuto.dll I have is 32-bit as well.
6. Navigate to Type Libraries | OPC Automation 2.0 (Ver 1.0)
7. Double click to view Type Library definition.
8. Do File | Save As... to D:\OPCDaAuto\OPCDaAuto.IDL.
9. Go back to the cmd.exe as per step 3. Change directory to D:\OPCDaAuto.
10. Fix OPCDaAuto.IDL
1. Compile the IDL file, like, midl /win32 OPCDaAuto.IDL /header OPCDaAuto.h 
2. This will fail about OPCGroups type specification.
3. Fix this by moving OPCGroups definition in line 188-195 to line 104, this is above OPC Server Object. Save the file, this will change the numbering.
4. Compile again as per sub-step 1 above.
5. This will fail again about single type specification. Change single to float for the lines as per the output of the compilation.
6. Compile again. This time it will complain about OPCGroup type specification.
7. Fix this by moving OPCGroup around line 255-262 to around line 196. This above definition of Collection of OPC Group Objects.
8. Compile again. This will fail again for another single data type. Convert it to float in 2 more places. Line location should be indicated in the compilation output.
9. Compile again. This time it should be successful.

Note that I haven't used the corresponding TLB and header files, yet. I am hoping it will work.