I'm curious if there is some attribute to indicate that some control's property is mandatory.

Imagine I'm a developer of a BaseValidator class which has ControlToValidate property. This property should never be left blank so I'd appreciate some RequiredPropertyAttribute class to denote this obligation. Compiler then could check if this property is present and set and otherwise raise an error.

Is there something to accomplish this?

Thanks, Borek

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Borek Bernard, http://borber.com

Me too (both developing validators and wanting an attribute to demand that it is required). Unfortunately, there is no attribute as requested. In my validators, when there is a required field that is not setup, I through an exception in the OnPreRender method to describe the problem.

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

PLBlum wrote:

Unfortunately, there is no attribute as requested.

I made a suggestion through product feedback center. You can vote for it here.

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Borek Bernard, http://borber.com

Great, Borek. I have voted for it.

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

The only way to guarantee that the property is set, is exactly what was previously suggested: Throw an exception at runtime (and yes, PreRender is a great place to do that).

One way to help guide users who are using your control is to use the ASP.net 2.0 / VS2005 feature called Smart Tasks. It's a great way to place common and/or important tasks right near your control so that the user won't be searching through the property grid to find two or three important properties out of 50. Here's a sample that I wrote recently:

http://www.leftslipper.com/ShowFaq.aspx?FaqId=7

Thanks,
Eilon

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Blog: http://weblogs.asp.net/LeftSlipper/

Eilon wrote:

The only way to guarantee that the property is set, is exactly what was previously suggested: Throw an exception at runtime (and yes, PreRender is a great place to do that).

Can you please elaborate why is PreRender so great place to do that? Why not do it in Init stage of page life cycle? (that's what I would do).

Thank you.

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Borek Bernard, http://borber.com

The reason for PreRender is that it happens after pretty much "everything else" happened. By that I mean that the page developer no longer has any practical events to handle to do interesting stuff, and other controls are done collecting their data. From PreRender and on the only things that happen are typically: building control trees, registering script/styles, and finally rendering.

Let's say you threw the exception in Init, then this scenario would be broken (and it's a fairly standard scenario):

<script runat="server">
   void Page_Load() {
      MyControl1.RequiredProperty = "Some Value";
   }
</script>
...
<foo:MyControl runat="server" id="MyControl1" />

By the time Page_Load happens and I want to set the required property, the control would have already thrown an exception and it would be too late. Lots of interactions happen up until PreRender so you typically want to give people as much chance as possible to set stuff up.

Thanks,
Eilon

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Blog: http://weblogs.asp.net/LeftSlipper/

Thanks for the answer. I realized all you've writter just a minute after I posted my question but I haven't written about it because I knew that your answer will be quicker than my post approval :) (yes, I'm one of those lucky moderated guys :)

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Borek Bernard, http://borber.com