HOWTO: Use OLE Automation from a C Application Rather Than C++ (181473)

MORE INFORMATION

1. Create a new "Win32 Console Application" project in Microsoft Visual C++ 5.0.
2. Add a Main.c (not Main.cpp) text file to your project.
3. Add the following code to your Main.c file:

         #include <stdio.h>
         #include <windows.h>
   
         void main(void) {
            IDispatch *pDisp; // Main IDispatch pointer.
            unsigned short *ucPtr; // Temporary variable to hold names.
            DISPID dispID; // Temporary variable to hold DISPIDs.
            CLSID clsid; // Holds CLSID of server after CLSIDFromProgID.
            HRESULT hr; // General error/result holder.
            char buf[8192]; // Generic buffer for output.
   
            // IDispatch::Invoke() parameters...
            DISPPARAMS dispParams = { NULL, NULL, 0, 0 };
            VARIANT parm1;
            DISPID dispidNamed = DISPID_PROPERTYPUT;
   
   
            // Initialize OLE Libraries.
            OleInitialize(NULL);
            {
               // Get CLSID for Excel.Application from registry.
               hr = CLSIDFromProgID(L"Excel.Application", &clsid);
               if(FAILED(hr)) {
                  MessageBox(NULL, "Excel not registered.", "Error",
                             MB_SETFOREGROUND);
                  return;
               }
               // Start Excel97, Excel 2000, or Excel 2002 and get its IDispatch pointer.
               hr = CoCreateInstance(&clsid, NULL, CLSCTX_LOCAL_SERVER,
                                     &IID_IDispatch, (void **)&pDisp);
               if(FAILED(hr)) {
                  MessageBox(NULL, "Couldn't start Excel.", "Error",
                             MB_SETFOREGROUND);
                  return;
               }
   
               // Get the 'visible' property's DISPID.
               ucPtr = L"Visible";
               pDisp->lpVtbl->GetIDsOfNames(pDisp, &IID_NULL, &ucPtr, 1,
                                            LOCALE_USER_DEFAULT, &dispID);
   
               sprintf(buf, "DISPID for 'Visible' property = 0x%08lx",
                       dispID);
               MessageBox(NULL, buf, "Debug Notice", MB_SETFOREGROUND);
   
               // Initiate parameters to set visible property to true.
               VariantInit(&parm1);
               parm1.vt = VT_I4;
               parm1.lVal = 1; // true
   
               // One argument.
               dispParams.cArgs = 1;
               dispParams.rgvarg = &parm1;
   
               // Handle special-case for property-puts!
               dispParams.cNamedArgs = 1;
               dispParams.rgdispidNamedArgs = &dispidNamed;
   
               // Set 'visible' property to true.
               hr = pDisp->lpVtbl->Invoke(pDisp,
                  dispID, &IID_NULL, LOCALE_SYSTEM_DEFAULT,
                  DISPATCH_PROPERTYPUT | DISPATCH_METHOD,
                  &dispParams, NULL, NULL, NULL
               );
               if(FAILED(hr)) {
                  sprintf(buf, "IDispatch::Invoke() failed with %08lx", hr);
                  MessageBox(NULL, buf, "Debug Notice", MB_SETFOREGROUND);
               }
   
               // All done.
               MessageBox(NULL, "done.", "Notice", MB_SETFOREGROUND);
            }
            // Uninitialize OLE Libraries.
            OleUninitialize();
   
         }
   					

4. Compile and run.