date formats

[Sam]

Hi,
In vb.net, I want to let the user enter a date format in a textbox.
e.g : mm/dd/yyyy
dd/mm/yyyy
dd-mm-yyyy

Then, how can I check this is a valid date format and how can I build
an example so that it is displayed in another textbox ?

12/31/2005

Regards

[Ken Tucker [MVP]]

Re: date formats

Hi,

Take a look at the datetime parse and parseexact methods

http://msdn.microsoft.com/library/de...parsetopic.asp

http://msdn.microsoft.com/library/de...exacttopic.asp

Ken
-------------------------
"Sam" <samuel.berthel ot@voila.fr> wrote in message
news:1117621293 .418433.290040@ z14g2000cwz.goo glegroups.com.. .
Hi,
In vb.net, I want to let the user enter a date format in a textbox.
e.g : mm/dd/yyyy
dd/mm/yyyy
dd-mm-yyyy

Then, how can I check this is a valid date format and how can I build
an example so that it is displayed in another textbox ?

12/31/2005

Regards

[Sam]

Re: date formats

Thanks but it's not exactely what I want.
Again I want to check that the string entered by the user (e.g
DD/MM/yyyy) is a valid date format and then prove it by displaying an
example (14/12/2005)

[Cor Ligthert]

Re: date formats

Sam,

Normally should the IsDate function be enough

Cor

[Ken Tucker [MVP]]

Re: date formats

Hi,

You could use a regex to check that it is a valid date format or
use a try catch block


Regex

Dim rValid As New System.Text.Reg ularExpressions .Regex("(0[1-9]|1[012])[-
/.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d")

If rValid.IsMatch( TextBox1.Text) Then

Dim dt As DateTime

dt = DateTime.Parse( TextBox1.Text)

TextBox2.Text = dt.ToLongDateSt ring

Else

MessageBox.Show ("Invalid date format")

End If




Try catch block

Try

Dim dt As DateTime

dt = DateTime.Parse( TextBox1.Text)

TextBox2.Text = dt.ToLongDateSt ring

Catch

MessageBox.Show ("Invalid date format")

End Try



Ken

--------------------

"Sam" <samuel.berthel ot@voila.fr> wrote in message
news:1117622372 .803107.123520@ g14g2000cwa.goo glegroups.com.. .

Thanks but it's not exactely what I want.
Again I want to check that the string entered by the user (e.g
DD/MM/yyyy) is a valid date format and then prove it by displaying an
example (14/12/2005)

[Cor Ligthert]

Re: date formats

Ken
[color=blue]
> You could use a regex to check that it is a valid date format
> or
> use a try catch block
>[/color]
In my opinion that is impossible the standard IsDate is very fine for that.

With using a regex you would allow in the first two 0-31 or test that
31-12 is allowed however
12-31 not

However the big problem is that you cannot do anything with that date. How
do you know what is
1-12-2005 without culture/language info info.

For you it is january 12 for me it is 1 december.

Cor

[Herfried K. Wagner [MVP]]

Re: date formats

"Sam" <samuel.berthel ot@voila.fr> schrieb:[color=blue]
> Again I want to check that the string entered by the user (e.g
> DD/MM/yyyy) is a valid date format and then prove it by displaying an
> example (14/12/2005)[/color]

I doubt that there is a way to check if a string is a valid date format,
because date format strings can contain arbitrary characters.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Sam]

Re: date formats

I haven't tried IsDate yet, but I have tried Ken's idea with the try
catch block :

Try
Dim dt As DateTime
dt = DateTime.Parse( "dddd - d - MMMM")
TextBox1.Text = dt.ToLongDateSt ring
Catch
MessageBox.Show ("Invalid date format")
End Try

However although dddd - d - MMMM is a valid format, it keeps raising an
exception :
The string was not recognized as a valid DateTime. There is a unknown
word starting at index 0.

Why that ?
Thx anyway for the replies guys

[Sam]

Re: date formats

Cor,
I've tried IsDate :

?isdate("dd mmm yyyy")
False
?isdate("mm/dd/yyyy")
False
?isdate("dd/mm/yyyy")
False
?isdate("dd-mm-yyyy")
False

Can you explain that to me ? Those should be valid date format !

[Sam]

Re: date formats

damn it.. I posted too quickly. Obviously IsDate expects a date, but
then it seems hard to convert the string format entered by the user to
a date... I'll try

[Sam]

Re: date formats

I think I've got it :) Using these function :
Note that MyDate.ToString will get what the user entered in my textbox.

Dim MyDate As New DateTime(2005, 12, 31)
Dim MyString As String = MyDate.ToString ("yyyy-MM-dd")

Dim res As Boolean = IsDate(MyString )

Thx

[Cor Ligthert]

Re: date formats

Sam,

As I wrote in this thread, the way dates are uses is depending on the
culture/language.

In Quibec it is the same as with us, however in Edmunton it is as in the
USA.

However I saw your latter message, therefore I assume you saw that already.

Cor

[Sam]

Re: date formats

Cor,
What if I want to check for any kind of regional settings ?

For example "MM/dd/yyyy" is not valid on my machine but "dd/MM/yyyy" is
valid, and I want both of them to be valid, how ?

Thx

[Herfried K. Wagner [MVP]]

Re: date formats

"Sam" <samuel.berthel ot@voila.fr> schrieb:[color=blue]
> I've tried IsDate :
>
> ?isdate("dd mmm yyyy")
> False
> ?isdate("mm/dd/yyyy")
> False
> ?isdate("dd/mm/yyyy")
> False
> ?isdate("dd-mm-yyyy")
> False
>
> Can you explain that to me ? Those should be valid date format ![/color]

'IsDate' is not intended for checking the validity of a date format string.
It's used to check the validity of a string representing a certain date.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Herfried K. Wagner [MVP]]

Re: date formats

"Sam" <samuel.berthel ot@voila.fr> schrieb:[color=blue]
> What if I want to check for any kind of regional settings ?
>
> For example "MM/dd/yyyy" is not valid on my machine but "dd/MM/yyyy" is
> valid, and I want both of them to be valid, how ?[/color]

AFAIS every string is a valid date format, but an infinite number of date
strings won't contain the date in a readable form.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>