How To Call a Script Function from a VC WebBrowser Application

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In order to call a script function that exists on a Web page, you have to use automation; in other words, IDispatch. Use the following steps to invoke a script function that exists on a Web page from your Visual C++ application:

1. Get the IDispatch of the HTML document.
2. Call IDispatch::GetIDsOfNames to get the ID of the script function.
3. Call IDispatch::Invoke to execute the function.

The following Visual C++ source code demonstrates how to implement this in your own application. This code uses smart pointers created by the #import statement. You must include this #import statement in one of your source code files, preferably Stdafx.h:

#import "C:\winnt\system32\mshtml.tlb" // location of mshtml.tlb

   void CMyClass::ExecuteScriptFunction()
   {
      // m_WebBrowser is an instance of IWebBrowser2
      MSHTML::IHTMLDocument2Ptr spDoc(m_WebBrowser.GetDocument());

      if (spDoc)
      {
         IDispatchPtr spDisp(spDoc->GetScript());
         if (spDisp)
         {
            // Evaluate is the name of the script function.
            OLECHAR FAR* szMember = L"evaluate";
            DISPID dispid;

            HRESULT hr = spDisp->GetIDsOfNames(IID_NULL, &szMember, 1,
                                           LOCALE_SYSTEM_DEFAULT, &dispid);

            if (SUCCEEDED(hr))
            {
               COleVariant vtResult;
               static BYTE parms[] = VTS_BSTR;

               COleDispatchDriver dispDriver(spDisp, FALSE);

               dispDriver.InvokeHelper(dispid, DISPATCH_METHOD, VT_VARIANT,
                                       (void*)&vtResult, parms,
                                       "5+Math.sin(9)");
            }
         }
      }
   }
				

The following is the HTML for the Web page that contains the evaluate function:

<HTML>
  <HEAD>
    <TITLE>Evaluate</TITLE>

    <SCRIPT>
      function evaluate(x)
      {
         alert("hello")
         return eval(x)
      }
   </SCRIPT>
  </HEAD>

  <BODY>
  </BODY>
</HTML>