Need help understanding regular expression

[Joe]

Hi,

I have been using a regular expression that I don’t uite understand to
filter the valid email address. My regular expression is as follows:

<asp:RegularExpressionValidator id="valValidEmail"
runat="server"
ControlToValidate="txtEmail"

ValidationExpression="^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$"
ErrorMessage="Invalid Email address."
Display="None">
</asp:RegularExpressionValidator>

Can someone explain me why the email address jo*******@Z-5com.com is
considered an invalid email address?

Also can someone explain me what the above regular expression means?

Thanks,

Joe

[Chris Hohmann]

"Joe" <Jo*@discussions.microsoft.com> wrote in message
news:35**********************************@microsof t.com...

Hi,

I have been using a regular expression that I don't uite understand to
filter the valid email address. My regular expression is as follows:

<asp:RegularExpressionValidator id="valValidEmail"
runat="server"
ControlToValidate="txtEmail"

ValidationExpression="^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$"
ErrorMessage="Invalid Email address."
Display="None">
</asp:RegularExpressionValidator>

Can someone explain me why the email address jo*******@Z-5com.com is
considered an invalid email address?

Also can someone explain me what the above regular expression means?

Thanks,

Joe

^ = Start of Line
([_a-z0-9-]+) = One or more underscores, alphanumeric or dashes
(\.[_a-z0-9-]+)* = Zero or more instances of the following; a period
followed by one or more underscores, alphanumeric or dashes
@ = the "at" sign
([a-z0-9-]+) = One or more alphanumeric or dashes
(\.[a-z0-9-]+)* = Zero or more instances of the following; a period followed
by one or more alphanumeric or dashes
(\.[a-z]{2,4}) = A period followed by 2, 3 or 4 letters.
$ = End of Line

[Tim Slattery]

Joe <Jo*@discussions.microsoft.com> wrote:

Hi,

I have been using a regular expression that I don’t uite understand to
filter the valid email address. My regular expression is as follows:

<asp:RegularExpressionValidator id="valValidEmail"
runat="server"
ControlToValidate="txtEmail"

ValidationExpression="^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$"
ErrorMessage="Invalid Email address."
Display="None">
</asp:RegularExpressionValidator>

Can someone explain me why the email address jo*******@Z-5com.com is
considered an invalid email address?

The RE doesn't allow upper-case letters, so the "Z" after the @ sign
is probably the culprit.

I can't tell from this snippet exactly how this RE is being applied.
VBScript's RegularExpression object has an "IgnoreCase" property. If
that's set to "true" before the "test" method is run then case doesn't
matter. This snippet doesn't tell me whether that's being done or not,
but I can't find any other reason for it to fail.

There's some Regular Expression documentation here:
http://msdn.microsoft.com/library/de...propattern.asp

Chris Hohmann's post describes what your RE is looking for. No need
for me to repeat that.

--
Tim Slattery
MS MVP(DTS)
Sl********@bls.gov