AJAX :: Validate Date If The User Doesn't Select From The CalendarExtender?

I populate the date field with DateTime.Today as the default date when the form loads in a TextBox then if the user wants

to change the date by clicking in the TextBox they can select a different date from the Calendar Extender that I have

connected to the TextBox so that they won't enter an incorrect date.

I tried to use an Ajax asp:MaskedEditExtender control along with the Calendar Extender, TextBox and default

date that is displayed but all of these things don't work together that way.

So the problem is that after the form loads the user still can enter an incorrect date if they highlight the TextBox

and type in a date into the TextBox instead of using the Calendar Extender to populate the TextBox.

I tried to use DateTime.TryParse to catch the bad date but DateTime.TryParse only catches some types of bad dates. For example:

99999999 will not get pass DateTime.TryParse

kkkkkkk will not get pass DateTime.TryParse

>>> However 1111/11/11 will get pass DateTimeParse but then when it tries to update the database it will give the error stating:

SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.

First the Date needs to be in the Format:

mm/dd/yyyy

Second 1111/11/11 if reversed is 11/11/1111 and is out of the range of what the error says the range is.

So my question is:

How can I get validate the date if the user doesn't select from the Calendar?

Below is the both html and code behind:

*** Below is the html:

<asp:SqlDataSource
ID="SqlIncomingForm"
runat="server" InsertCommandType="Text" OnInserting="SqlIncomingForm_Inserting" OnInserted="SqlIncomingForm_Inserted"
ConnectionString="<%$ ConnectionStrings:IncomingForm %>"

[Code]....