C / C++ / MFC

1. For a file extension "doc", open HKEY_CLASSES_ROOT\.doc Look at the default value. It's a part key name, for instance Word.Document.8. Also, HKEY_CLASSES_ROOT\.doc may contain information such as content type (mime) worth collecting
   
2. Assuming the key name was Word.Document.8, open HKEY_CLASSES_ROOT\Word.Document.8
   
3. Collect the data you want from here (default icon, file type descriptions, etc.)
   

SHFILEINFO sfi = {0};
 
  SHGetFileInfo ( _T("foo.dll"), FILE_ATTRIBUTE_NORMAL,
                  &sfi, sizeof(SHFILEINFO), 
                  SHGFI_USEFILEATTRIBUTES | SHGFI_ICON |
                    SHGFI_LARGEICON );
 
// now sfi.hIcon holds the 32x32 icon

You see the Standards change. - Fellow co-worker

myDialog.Invalidate();
myDialog.UpdateWindow();

CString String1 = "C://files";
CString String2 = "data.txt";

CString Result = String1 + "/" + String2;

char final_result[20];

if (Result.GetLength() < (sizeof(final_result) - 1)) {
    strcpy(final_result,Result);
}
else {
    // signal error
}