/// <summary>
/// Enumerates all installed Common Language Runtime Engines.
/// </summary>
/// <param name="Index">Zero-based index of looked runtime record.</param>
/// <returns>True if runtime with specified index found.</returns>

function EnumInstalledRuntimes(Index: Integer; out VersionName: String): Boolean;
var
  hkey: Windows.HKEY;
  hsubkey: Windows.HKEY;
  I: Cardinal;
  J: Cardinal;
  NameBuf: array[0..MAX_PATH] of Char;
  CNameBuf: Cardinal;
  lwt: TFileTime;
  vt: DWORD;
  AnyFound: Boolean;
begin
  Result := False;
  VersionName := '';
  if ERROR_SUCCESS = RegOpenKeyEx(HKEY_LOCAL_MACHINE, PChar('SOFTWARE\Microsoft\.NETFramework\policy'), 0, KEY_ENUMERATE_SUB_KEYS, hkey) then
  try
    I := 0;
    while True do
    begin
      AnyFound := False;
      CNameBuf := MAX_PATH + 1;
      if ERROR_SUCCESS <> RegEnumKeyEx(hkey, I, @NameBuf[0], CNameBuf, nil, nil, nil, @lwt) then
      begin
        Break;
      end;
      if (NameBuf[0] = 'v') and (NameBuf[1] in ['1'..'9']) then
      begin
        VersionName := String(NameBuf);
        if ERROR_SUCCESS = RegOpenKeyEx(hkey, @NameBuf[0], 0, KEY_QUERY_VALUE, hsubkey) then
        try
          J := 0;
          while true do
          begin
            CNameBuf := MAX_PATH + 1;
            if ERROR_SUCCESS <> RegEnumValue(hsubkey, J, @NameBuf[0], CNameBuf, nil, @vt, nil, nil) then
            begin
              Break;
            end;
            if (vt = REG_SZ) and (NameBuf[0] <> #0) then
            begin
              VersionName := VersionName + '.' + String(NameBuf);
              AnyFound := True;
              Break;
            end;
            Inc(J);
          end;
        finally
          RegCloseKey(hsubkey);
        end;
      end;
      Inc(I);
      if AnyFound then
      begin
        if Index = 0 then
        begin
          Result := True;
          Break;
        end;
        Dec(Index);
      end;
    end;
  finally
    RegCloseKey(hkey);
  end;
end;