I'd like to subclass off the RegularExpressionValidator control and add one additional feature: a required field check. The MS regular expression should take care of this, but it doesn't. So I'd simply like to add a design-time property 'Required', and override the validation method and add this additional check in. My problem is: where's the documentation to find the appropriate validation method to override? And what the protected variable names are, for instance to access the ControlToValidate.Text value?

Thanks!

buzz

You don't need to make a control for that. There is no problem in putting two validators for one control. So, you can put a RequiredFieldValidator and a RegularExpressionValidator for the control you want to check. You can link as many validators as you want to a control.

<asp:TextBox id="txtField" runat="server" />
<asp:RequiredFieldValidator ControlToValidate="txtField" Text="The field is empty!" runat="server" />
<asp:RegularExpressionValidator ControlToValidate="txtField" Text="The text is invalid!" ValidationExpression="P[0-9]" runat="server" />

Thanks, but that's the whole point - I don't want to have to put 2 controls on the form. Why should I have to? It really peeves me that the MS regular expression validator doesn't follow regular expressions in this regard. A regex expression can explicitly dictate that the value must be 1 or more characters long, but the MS control allows it anyway. A direct violation of the regular expression, no? Why does it do this? Or am I missing something? If it's just the error message that's the issue, why not just put an 'RequiredFieldErrorMessage' property in there as well so you'd have separate messages?

Anyhow, that's why I'm doing this, I just think it's really clunky to have to put down 2 validator controls for each field.

Thanks for your help!!

buzz

you're mixing the concept of format checking and required checking. i say if it works for you, do it.

what i might suggest in your case is making a TextBox that incorporates all of that functionality. then you don't even have to add in the validators. i've done it and it saves a great deal of time in setting up a form. it's surprisingly easy.

Mixing, I guess that's one way to put it, but the fact remains that the regular expression is not followed correctly by the Microsoft control, right? If it was accurately following the regex then it wouldn't allow a blank value when the expression has {1,} in it. That's the only reason why I need a separate required field validator.

That's a great idea of putting it in the TextBox, but how do I keep from having to duplicate all the RegularExpressionValidator functionality?

Thanks!

buzz

the MS implementation of the regex check is a bit messed up, but the blank value not eliciting a validation error is logical. that's why the required validator exists. there is a logical difference between format checking and required checking: one does not necessarily require the other. (i don't like that i am defending the MS validators since i think they aren't so great.)

there are really only a few properties you would need to expose (more than likely) in building it all into the textbox. i'd say expose them as you need them. for example, do you really need all the font settings when you can simply set the CssClass? i think i only ever exposed the ValidationExpression and ErrorMessage properties since i was tightly controlling the styles.

I would agree with you if regular expressions didn't already cover the blank/non-blank idea, but they do. There is syntax in regular expressions that specify whether a value can be blank or not. But the MS implementation chooses to ignore this. Not exactly out of character for MS, but wrong nonetheless IMHO :).

Anyhow, I like your idea of the TextBox, but I still don't understand: how do I get the validation functionality? Are you talking about a composite control or something?

buzz

the textbox can contain child controls which are your validators. if you concentrate on overriding the existing methods, the whole thing is pretty tidy (as in not too much code). override the CreateControlCollection method to return a new control collection. in CreateChildControls, you add the validators to the TextBox's control collection. i think the next step is overriding the render method to make sure the controls render *after* the input box.

if you get stuck, post a note back here and i'll give you some code snippets.

by your logic, using regular expressions on a non-required field means my expression must now be altered to allow for blanks. they are conceptually two different validations. what you want is a shortcut, which is fine in your case, but is not appropriate for general development. i've built validation frameworks before and they always separate regular expression validation (or any other type) from required field validation.

hlaford -

Child controls, eh? Didn't know you could do that. I'll give that a try, thanks!

Hmm.. not sure why I'm seeing this so different from you (and Microsoft!)...

Absolutely, the regular expression should be altered to allow for blanks! The alternative is that the control violates any regular expression that specifies a non-blank value. And that's what it does now. How are they 'conceptually different' if regular expressions also include the idea of preventing non-blank fields? The idea of non-blank values is fully supported in regular expressions, it's just ignored by this control. To me this is the strange part. I'm not sure why someone would think it shouldn't. Is the thinking that it's an inconvenience to have to work that into the expression, so that the validation string is simpler? Maybe that's what I've been missing. But the fact remains that in doing this the control violates regular expressions. Aren't we programmers? We're not supposed to like exceptions to rules, don't we like consistency and elegance? But here it's just *poof* and we ignore one of the rules of regular expressions...

Don't know why I'm getting so worked up over this stupid issue.... for some reason I find it quite irritating!! But isn't that what these forums are for? :)

Thanks!

buzz

the best way i can think to describe my meaning is that regexes describe a format rather than a presence of a text value. as an example, let's take a textbox that takes a value of a US social security number. the regex i would use is

^\d{3}(-?)\d{2}\1\d{4}$

let's ignore the fact that MS regex validation processing doesn't require the ^ and $ (which is a peeve of mine). if my textbox value isn't required, how do i write that expression?

^(\d{3}(-?)\d{2}\2\d{4})?$

i've just complicated the expression in order to account for that requirement. i cannot now alter the required status of the field without changing the expression i'm using. the first regex defines the format i expect for a SSN; the second is a bastardization of that format to handle a special case that isn't actually a format requirement.

i don't think i'm explaining myself very well here.

Actually you are explaining quite well. I see your point, but I still can't get past the fact that the control ignores part of the regex specification. I understand they have a control dedicated to required fields, but does that mean that they drop support for part of the regular expression specification? Shouldn't I decide whether I want the regex to include/exclude the notion of a blank field? They take that choice right out of my hands and force me to use a 2nd control.

Here's a an analogy: I create a "table-cell-alignment" control. Any time you want to align the contents of a table cell, you need to use my control in a cell. "But", you say, "there's already an HTML spec for alignment in a cell!". To this I say, "too bad, I think it's better for you to use my control so I'm going to ignore the "align" attribute in a <TD> definition".

Might not be a perfect analogy, but conceptually it's the same. They choose to ignore the spec because they have their own approach. As I said before, not exactly out of character for MS, but frustrating! (I happen to respect MS greatly in most things, by the way) This is all academic, of course, I'll survive and use 2 controls, but I do find it an interesting subject for some reason.

buzz

well, you could still create your own validator that does what you want. MS isn't preventing it; they just didn't give it to you.

True enough, when I get the time I'll create new control. Or I might buy Peter Blum's validation controls, they're only $50, but it's $50 per application, so gotta think about that one. Thanks for your feedback, hlaford, you got me thinkin' and I appreciate it.

Buzzripper,

You indicated that my Professional Validation And More is $50 per application. That's incorrect. Its $50 per production server, covering all web apps on that server. In addition, I don't charge for development servers. The purchase of one production server license (called a Web Server License) covers all non-production servers. If you have 5 or more production servers, purchase a Site License at $250. If you are building a web app for redistribution, purchase a Redistribution License for $500. It covers your site plus every web app you generate for an unlimited number of customers. I think you'll find this pricing is exceptionally low in this marketplace.
Learn more at http://www.PeterBlum.com/VAM/Home.aspx.

---

--- Peter Blum
Creator of Professional Validation And More Suite, Peter's Date Package, and Peter's Polling Package
www.PeterBlum.com

I apologize if I mis-characterized your pricing. Each of my apps will go on a different production server (I'm a contractor), so for my purposes it is $50 per app. But if you're running more than one app on a server, you're absolutely correct it is not $50 per app.

Sorry again if I gave the wrong impression. It was not my intention to mislead anyone. In fact, the reason I even mentioned your product was because I have taken a look at your product and like it very much. It's extremely flexible and powerful and I may in fact buy it. I was just thinking aloud, so to speak.

buzz