Validating a date in a compound IF statement

[nclrwntr]

I need to validate a date entered into a textbox in the form mm/dd/yy by using a massive compound IF statement. If the date is valid, nothing happens but if an invalid date is entered, a message box pops up saying, "invalid date."

 

this is what I have so far:

 

fulldate= txtdate.text
month = fulldate.Substring(0, 2)
day = fulldate.Substring(3, 2)
year = fulldate.Substring(6, 2)

If (month < 1 Or month > 12) Or (day < 1 Or day > 31) Or (year > 3 And year < 38) Or (month = 4 And day > 30) Or (month = 6 And day > 30) Or (month = 9 And day > 30) Or (month = 11 And day > 30) Then
           MsgBox("Invalid Date Entered", , "Data Entry Error")
           Exit Sub
       End If

 

I've tried a lot of different things to do the leapyear and non leapyear calculations but nothing works.

 

I can make it work using mod operators but we can't use them.

Edited February 28, 2003 by nclrwntr

[Volte]

You can use the IsDate function.

If Not IsDate(fullDate) Then
 MessageBox.Show("Invalid Date!")
End If

[nclrwntr]

lol. I forgot to mention that I'm prohibited from using that as well.:)

 

And it doesn't seem to work.

Edited February 28, 2003 by nclrwntr

[Volte]

In that case, you will need to do some work. Date parsing is a very

complicated thing, in that you can have many different formats,

orders, styles, delimiters and not to mention leap years...

 

In my eyes, this exercise is needlessly complicated, but then again

I'm not the instructor. :-\

[nclrwntr]

Here, here. there are easier ways but we can't use them since we haven't covered it yet. blech!

[bpayne111]

Not that this is totally relevant to your question but...

you should try the OrElse statement instead of Or

The OrElse statement will return true with the first expression that is true.

The Or statement on the other hand will evaluate all of the expressions regaurdless of thier value taking more time than the previous example.

Sometimes Or is the correct logic operator to use if you for instance wanted to evaluate a function reguardless of it's return value. In this case the OrElse statement may terminate before the Function is evaluated.

 

I taught my teacher that one... hehehehe

I can type you up some sample code if you like

[bpayne111]

OH by the way if you are subtracting dates by chance the DateDiff function may be of use to use to you

[nclrwntr]

Thanks for the help bpayne.:)

[bpayne111]

anytime

[CaNaDiAn BaCoN]

This works, but...

 

This expression should provide the result you want, if you're allowed to use it

DateTime.IsLeapYear(CInt(year))

[Nerseus]

I assume you can't use DateTime.Parse(...) either?

 

I believe the "IsLeapYear" function checks the following:

if(year is evenly divisible by 4 and NOT 0, 1000, 3000, 5000, etc.)

leap year!

else

not leap year!

 

Since this seems to be an excercise, I'm not providing the details just the info :)

 

-Nerseus

[nclrwntr]

Thanks for the input all!:)

 

I've decided to go with "year mod 4 = 0" style.

 

Bottome line is that it works right? He should accept this. I hope........

 

The only reason why he wouldn't is because we haven't learned it yet in class but I figured it out on my own. That counts for something.:)

[Nerseus]

Don't forget that every other 1000 years is NOT a leap year though it is evenly divisible by 4. So 1000 mod 4 = 0 but 1000 is not a leap year (2000 is, 3000 isn't, etc.)

 

-Nerseus

[nclrwntr]

yup got that too. div by 4 but not if div by 100 but yes if div by 400