//
// Problem Category Index
//
public static void DownloadCategoryIndex()
{
//problem category index
string url = "https://raw.githubusercontent.com/dipu-bd/uva-problem-category/master/data/INDEX";
string file = LocalDirectory.GetCategoryIndexFile();
DownloadFileAsync(url, file, null, Priority.Normal,
__DownloadCategoryIndexProgress, __DownloadProblemCategoryCompleted, 1);
}