Protected WithEvents
RegularExpressionValidator1 As System.Web.UI.WebControls.RegularExpressionValidator
The rest is as easy as 1,2,3.
1. First I drop a text box on my form. This is where I enter
my test expression. I'll give the control an id of "txtText".
<asp:TextBox id="txtTest" runat="server"> </asp:TextBox>
2. Next I drop a RegularExpressionValidator control on the
form. I give this control an id of "RegularExpressionValidator1" since
I'm not feeling very creative today. I set the "ControlToValidate"
property to the id of the control I want to validate (which is the
textbox I just created). I set the "ErrorMessage" property to what
I want to display if the expression is not valid. I set the "ValidExpression"
property to a regular expression that I want to use to compare against
the input. In this case, I've just set the expression to the letter
"m".
<asp:RegularExpressionValidator id="RegularExpressionValidator1"
runat="server" ControlToValidate="txtTest"
ErrorMessage="Sorry. You are not a valid expression!"
ValidationExpression="m"> </asp:RegularExpressionValidator>
3. Next I drop a button control on the form. This is just so
we have a place for the cursor to go after we leave the textbox.
<asp:Button id="Button1" runat="server"
Text="Submit"> </asp:Button>
Now we are ready to test our control that should only allow the letter
"m" (lower case) to get by. If we enter "m" and press TAB or click
the SUBMIT button, everything looks good - no error messages. If we
leave the textbox blank, there is no error message either because
the control only checks input that exists, not the existence of input.
If, however, we enter any other character or digit the conrol's error
message will be displayed. In this case, the error message is "Sorry.
You are not a valid expression!"
Now that we know how to use the control, what we really need is a
primer on regular expressions. Then we can easily drop a RegularExpressionValidator
control on our form, associate it with an entry in a text box and
set the "ValidationExpression" property to what we want the input
to look like.
Regular Expressions
The subject of regular expressions is often confusing but we are going
to take an approach that will give you a basic understanding upon
which you can build. Becoming proficient with regular expressions
takes a lot of practice, just like anything else.
Regular expressions let us to search for certain patterns. In the
case of our validator control, if we find the pattern in the textbox,
the control is satisfied and let's the text through to the promise
land. If we do NOT find that pattern, the control is not happy and
displays its error message. (This is not all we can do with regular
expressions. We can also "search and replace" and reformat text. Just
be aware that you can use regular expressions to find all instances
of some word or phrase and replace it with another or reformat it.
You can use them to mine documents for email addresses or URL's. I'll
discuss that more fully in a future article.)
Character Matching
The easiest kind of matching we can do is "character matching". That's
what we did when we put the letter "m" in our validator control. We
are simply asking if the text is the letter "m" and nothing else.
So the lowercase letter "m" passes but the uppercase "M" does not.
If you enter "mom", it does not pass because "mom" is not "m" - it
is something more than just "m".
Character matching is not limited to a single character. If you use
the regular expression "mom" then the only expression that matches
will be "mom". "MOM" will not work, "mommy" will not work and "I want
my mom" will not work because none of these expressions is exactly
equivalent to "mom". OK, I think we are clear on that point.
A period is a special character that matches any single character.
So the regular expression "m.m" would match "mom" or "mam" or "m9m".
need help asap with asp!!!!
Hi, I created a search page, search.asp for a website http://www.patentlawbooks.com but I cannot make it work.
My database name is 'bookstore' my table name is 'table2'. It is a dsn less connection.
The code for the search page is : ...
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You can search for a string that has a single character from a group
of predetermined characters. For example: "m[ao]m" would match up
with "mam" or "mom" because the middle letter is in the group [ao],
but "m9m" would not match because "9" is not an "a" or an "o".
You can search for a string that has a single character that is in
a range. For example: "m[a-y]m" will match up with "mam" or "mbm"
or "mcm" or any other letter in the middle so long as it is in the
range [a-y]. The letter "z" is not in that range and all uppercase
letters are not in that range.
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About the Author:
Visit Roger McCook's Web site at http://www.mccooksoftware.com.
Read this newsletter at: http://www.webproasp.com/2003/0922.html |
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By
Roger McCook
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