Launch a URL in a tab in an existing IE window from C#

Using shdocvw library (add reference to it, you can find it in windows\system32) you can get the list of instances and call navigate with the newtab parameter:

ShellWindows iExplorerInstances = new ShellWindows();
if (iExplorerInstances.Count > 0)
{
  IEnumerator enumerator = iExplorerInstances.GetEnumerator();
  enumerator.MoveNext();
  InternetExplorer iExplorer = (InternetExplorer)enumerator.Current;
  iExplorer.Navigate(url, 0x800); //0x800 means new tab
}
else
{
  //No iexplore running, use your processinfo method
}

---

Edit: in some cases you may have to check if the shellwindow corresponds to a real iexplorer an not to any other windows shell (in w7 all instances are returned, don’t know now for others).

   bool found=false;
   foreach (InternetExplorer iExplorer in iExplorerInstances)
   {
       if (iExplorer.Name == "Windows Internet Explorer")
       {
           iExplorer.Navigate(ur, 0x800);
           found=true;
           break;
       }
   }
   if(!found)
   {
      //run with processinfo
   }

You may also find these additional IE Navigate Flags useful. Full description of the flags are available at http://msdn.microsoft.com/en-us/library/dd565688(v=vs.85).aspx

enum BrowserNavConstants 
{ 
    navOpenInNewWindow = 0x1, 
    navNoHistory = 0x2, 
    navNoReadFromCache = 0x4, 
    navNoWriteToCache = 0x8, 
    navAllowAutosearch = 0x10, 
    navBrowserBar = 0x20, 
    navHyperlink = 0x40, 
    navEnforceRestricted = 0x80, 
    navNewWindowsManaged = 0x0100, 
    navUntrustedForDownload = 0x0200, 
    navTrustedForActiveX = 0x0400, 
    navOpenInNewTab = 0x0800, 
    navOpenInBackgroundTab = 0x1000, 
    navKeepWordWheelText = 0x2000, 
    navVirtualTab = 0x4000, 
    navBlockRedirectsXDomain = 0x8000, 
    navOpenNewForegroundTab = 0x10000 
};