String to Date conversion

Im trying to convert the input of several dropdownlists into a Date, but I can get an error and dont know how to convert these fields to a date type...
This is the code:
Dim BirthDate As DateTime = CType(ddlDay.SelectedValue + ddlMonth.SelectedValue + ddlYear.SelectedValue, Date)
And now im here anyways :p ...how can I calculate someones age when I have his birth date?

It would probably be best if you keep the two types the same. Try using this:

Dim BirthDate As DateTime = CType(ddlDay.SelectedValue & "/" & ddlMonth.SelectedValue & "/" & ddlYear.SelectedValue, DateTime)

Try using something like this, for the calculation (assuming a sub, based on a button's click event):

Sub getDiff(Source as Object, E as EventArgs)
Dim myBirth as DateTime
Dim sDate as String
Dim Age As Integer
sDate=ddMonth.SelectedItem.Value & "/" & ddDay.SelectedItem.Text & "/" & ddYear.SelectedItem.Text
myBirth=cDate(sDate)
Age=DateTime.Now.Year - myBirth.Year
If DateTime.Now.Month < myBirth.Month Or (DateTime.Now.Month = myBirth.Month And DateTime.Now.Day < myBirth.Day) Then
Age = Age - 1
End If
lblDate.text="Age=" & Age.ToString
End Sub

Check out full code sample:
http://aspnet101.com/aspnet101/aspnet/codesample.aspx?code=calcage

Hi Peter Smith,

Give the following a try. Example:

Dim tempAsString = ddlDay.SelectedValue + "/" + ddlMonth.SelectedValue + "/" + ddlYear.SelectedValue
Dim birthDateAs DateTime = DateTime.Parse(temp)

The following function can be used to calculate Age, given a BirthDate. Example:

Public Shared Function Age(ByVal dateOfBirth As DateTime) As Integer
If DateTime.Today.Month < dateOfBirth.Month Or DateTime.Today.Month = dateOfBirth.Month And DateTime.Today.Day < dateOfBirth.Day Then
Return DateTime.Today.Year - dateOfBirth.Year - 1
Else
Return DateTime.Today.Year - dateOfBirth.Year
End If
End Function

Hope this helps.