// random select m numbers from total
public static List <int> RandomSelect(int m, int total)
{
byte[] seed = BytesHelper.GenRandomBytes(256);
var cache = new List <KeyValuePair <int, int> >();
for (int i = 0; i < total; i++)
{
//int hash = BitConverter.ToInt32(Sha256(BitConverter.GetBytes(i + 1).Concat(seed)), 0);
int hash = BitConverter.ToInt32(seed, i % 224) ^ (i + 1);
cache.Add(new KeyValuePair <int, int>(i + 1, hash));
}
return(cache.OrderBy(p => p.Value).Take(m).Select(p => p.Key).ToList());
}