calculate current age from date of birth

Protected Sub btn_Click(sender As Object, e As EventArgs)
    ' here you use your ddl,combobox or etc where age date is inserted
    Dim dtStart As DateTime = DateTime.Parse(txtDoB.Text)
    Dim sp As TimeSpan = DateTime.Now - dtStart
    Dim year As Integer = "18"
    Dim days As Integer = 365
    Dim total As Integer = year * days

    If sp.Days < total Then

        txtDoB.Text = "Not Valid"
        lblMess.Text = "You can not be under 18 years"
        Return
    End If
End Sub

Hope I help you.

Try this:

Dim strDOB As String
strDOB = txtDateOfBirth.TextDim 
intAge As Integer
intAge = Math.Floor(DateDiff(DateInterval.Month, DateValue(strDOB), Now()) / 12)
lblAge.Text = intAge

protected void btn_Click(object sender, EventArgs e)
    {
string dt=combobox1.selectedvalue+"/"+combobox2.selectedvalue+"/"+
combobox3.selectedvalue;
System.DateTime dateOfBirth=Convert.ToDateTime(dt);
TimeSpan ts=new TimeSpan();
System.DateTime currentDate=DateTime.Now();
ts=currentDate.Subtract(dateOfBirth);
int years=0;
int months=0;
int days=0;
years=(ts.Days/366);

DateTime workingDate = dateOfBirth.AddYears(years);


//calculation of months 
ts= currentDate - workingDate;
months = timeSpan.Days / 31;
workingDate = workingDate.AddMonths(months);


//calculation of days
days = currentDate.Subtract(dateOfBirth.AddYears(years).AddMonths(months)).Days;

TextBox1.Text=concatenate the values of years,months and days which you get from above.

      

}

Also, you need to take into considerations some special conditions such as the date of birth is 31/12/2012 and the currentdate is 01/01/2013...some conditions need to be checked...have a look at that...I dont remember those now.

The above code will accept values from all the 3 combo boxes in a string variable and then a TimeSpan object will calculate the diff between current date and the date of birth.
Also the highest entity which TimeSpan() shows is the number of days..Hence we need to multiply the TimeSpan diff with enitity "Days" and divide it by 366 to get the number of years..

Hope the above helps...


Converted In VB

Protected Sub btn_Click(sender As Object, e As EventArgs)
    Dim dt As String = (combobox1.selectedvalue + combobox2.selectedvalue & "/") + combobox3.selectedvalue
    Dim dateOfBirth As System.DateTime = Convert.ToDateTime(dt)
    Dim ts As New TimeSpan()
    Dim currentDate As System.DateTime = DateTime.Now()
    ts = currentDate.Subtract(dateOfBirth)
    Dim years As Integer = 0
    Dim months As Integer = 0
    Dim days As Integer = 0
    years = (ts.Days / 366)
    Dim workingDate As DateTime = dateOfBirth.AddYears(years)
    ts = currentDate - workingDate
    months = timeSpan.Days / 31
    workingDate = workingDate.AddMonths(months)
    days = currentDate.Subtract(dateOfBirth.AddYears(years).AddMonths(months)).Days
End Sub

regards
-anurag