code for find first and last saturday of current months

Linq way is practical and easy, this is the classical method if anyone needs a non linq method;

public static Tuple<DateTime,DateTime> GetFirstAndLastSaturday()
{
    var curDate = DateTime.Now;
    var firstSaturday = new DateTime(curDate.Year,curDate.Month,1);
    while (firstSaturday.DayOfWeek != DayOfWeek.Saturday)
    {
       firstSaturday = firstSaturday.AddDays(1);
    }
    var lastSaturday = firstSaturday;
    while (lastSaturday.AddDays(7).Month == curDate.Month)
    {
        lastSaturday = lastSaturday.AddDays(7);
    }

    return new Tuple<DateTime, DateTime>(firstSaturday,lastSaturday);
}

var result = GetFirstAndLastSaturday();

It's easiest if you let the DateTime class do the work.

Use the 1st day of the month and calculate to next Saturday. Use the 1st day of the next month and calculate to previous Saturday.

private void onDtPickerValueChanged(object sender, EventArgs e)
{
	DateTimePicker dtPicker = (DateTimePicker)sender;
	int firstSaturday = 0;
	int lastSaturday = 0;

	getFirstLastSatuday(dtPicker.Value, out firstSaturday, out lastSaturday);
	System.Diagnostics.Debug.WriteLine("First Saturday = {0}, Last Saturday = {1}",
		firstSaturday, lastSaturday);
}

private static void getFirstLastSatuday(DateTime date, out int firstDay, out int lastDay)
{
	DateTime dateTime = new DateTime(date.Year, date.Month, 1);
	int dayofWeek = (int)dateTime.DayOfWeek; // Sunday = 0, Saturday = 6
	firstDay = 1 + (6 - dayofWeek);

	dateTime = dateTime.AddMonths(1);
	dayofWeek = (int)dateTime.DayOfWeek;
	lastDay = dateTime.AddDays((dayofWeek + 1) * -1).Day;
}

This method computes the first and last Saturday of the current month.

DateTime firstDate = DateTime.Parse(DateTime.Now.Year.ToString () + "/" + DateTime.Now.Month.ToString () + "/01");
DateTime lastDate; // Last date of the Current Month
int intDiff;
DateTime firstSaturday; // First Saturday of the Current Month
DateTime lastSaturday;   // Last Saturday of the Current Month
//
// Compute First Saturday
intDiff= 6 - (int)firstDate.DayOfWeek;
firstSaturday = firstDate.AddDays(intDiff); 
//
// Compute Last Date of the Current Month 
lastDate = firstDate.AddMonths(1).AddDays(-1);  
//
// Compute Last Saturday of the Current Month
intDiff = 6 - (int)lastDate.DayOfWeek;
if (intDiff == 0)
{
    lastSaturday = lastDate;
}
else
{
    lastSaturday = lastDate.AddDays(-(7 - intDiff));
}
//
//
Debug.WriteLine("First Saturday={0}", firstSaturday);
Debug.WriteLine("Last Saturday={0}", lastSaturday);