public string nextMa(string str)
{
BUS_GIAIDAU temp = new BUS_GIAIDAU();
//get last matk
DataTable t = temp.topGIAIDAU();
string Tmag = t.Rows[0].Field <string>(0);
//get int in a string to add 1 after string
string mastr = Regex.Match(Tmag, @"\d+").Value;
int ma = Int32.Parse(mastr);
ma++; mastr = null;
mastr += str; mastr += ma;
return(mastr);
}