how to calculate age

hey i am not an expert but try this code maybe its too lengthy and may have lots of if-nested-if loops but i think even a beginner can understand this code quickly

first i am doing this code to accept a text of date of birth in one textbox and display age on another textbox as soon as the date of birth is enetered

lets take the textbox which date of birth has to be entered as txtDateofBirth and that to display age as txtAge
so we have to display age when text is changed in txtDateofBirth

protected void txtDateofBirth_TextChanged1(object sender, EventArgs e)
    {
        DateTime dob = Convert.ToDateTime(txtDateofBirth.Text); //convert the inputtext to date format ie of dd/mm/yyy
        int myYear = dob.Year;//getting year of date of birth
        int myMonth = dob.Month;//getting month of date of birth
        int myDay = dob.Day;//getting day of date of birth
        int currentYear = DateTime.Now.Year;//getting current year
        int currentMonth = DateTime.Now.Month;//getting current month
        int currentDay = DateTime.Now.Day;//getting current day
        int Age = currentYear - myYear;//calculating age in a general approach
        if (currentMonth >= myMonth)
        {
            if (currentMonth == myMonth)
            {
                if (currentDay > myDay)
                {
                    txtAge.Text = Convert.ToString(Age);
                }
                else
                {
                    txtAge.Text = Convert.ToString(Age - 1);
                }
            }


            else
            {
                txtAge.Text=Convert.ToString(Age);
            }

            }
        else
        {
            txtAge.Text=Convert.ToString(Age-1);
        }
        }
    }

so you must enable autopostback of txtDateofBirth To get the age quickly
this is my first solution so sorry if it is too lengthy