C # Calculation of the date and month days and the number of weeks in a year and the time period obtained by a certain week of the year

How many days are there in the current month
</summary>
<param name= "Y" ></param>
<param name= "M" ></param>
<returns></returns>
public static int Howmonthday (int y, int m)
{
int mnext;
int ynext;
if (M < 12)
{
Mnext = m + 1;
Ynext = y;
}
Else
{
Mnext = 1;
Ynext = y + 1;
}
DateTime dt1 = System.Convert.ToDateTime (y + "-" + M + "-1");
DateTime DT2 = System.Convert.ToDateTime (Ynext + "-" + Mnext + "-1");
TimeSpan diff = dt2-dt1;
Return diff. Days;
}

/**////<summary>
Get the start date and deadline of a week in a year
Year Nyear
Week number Nnumweek
Week start out Dtweekstart
Week End out Dtweekeend
</summary>
<param name= "Nyear" ></param>
<param name= "Nnumweek" ></param>
<param name= "Dtweekstart" ></param>
<param name= "Dtweekeend" ></param>
public static void Getweek (int nyear, int. Nnumweek, Out datetime dtweekstart, out datetime dtweekeend)
{
DateTime dt = new DateTime (Nyear, 1, 1);
DT = dt + new TimeSpan ((nNumWeek-1) * 7, 0, 0, 0);
Dtweekstart = dt. AddDays (-(int) dt. DayOfWeek + (int) dayofweek.monday);
dtweekeend = dt. AddDays ((int) dayofweek.saturday-(int) dt. DayOfWeek + 1);
}

       /**////<summary>
        ///How many weeks in a year
       //return int
        //</summary>
       //<param name= "Stryear" ></ Param>
       //<returns>int</returns>
         public static int getyearweekcount (int stryear)
         {
            string returnstr = "";

            System.DateTime fDt = DateTime.Parse ( Stryear.tostring () + "01-01");
            int k = Convert.ToInt32 (Fdt.dayofweek);// The first day of the year is the   of the week;
            if (k = = 1)
             {
                 int countday = fdt.addyears (1). AddDays (-1). DayOfYear;
                int countweek = COUNTDAY/7 + 1;
                return countweek;

}
Else
{
int countday = Fdt.addyears (1). AddDays (-1). DayOfYear;
int Countweek = COUNTDAY/7 + 2;
return countweek;
}

}

/**////<summary>
Ask the current date is the first week of the year
</summary>
<param name= "Date" ></param>
<returns></returns>
public static int WeekOfYear (DateTime curday)
{
int firstdayofweek = Convert.ToInt32 (Convert.todatetime (curDay.Year.ToString () + "-" + "1-1"). DayOfWeek);

int days = Curday.dayofyear;
int daysoutoneweek = days-(7-firstdayofweek);

            if (daysoutoneweek <= 0)
             {
                 return 1;
           }
            Else
             {
                 int weeks = DAYSOUTONEWEEK/7;
                if ( Daysoutoneweek% 7! = 0)
                     weeks++;

return weeks + 1;

}

}

C # Calculation of the date and month days and the number of weeks in a year and the time period obtained by a certain week of the year