Displaying an alert when a validator fails

Hi All,

I've got a RangeValidator that ensures that the integer input in a textbox is in the allowed range.  It pops up some red error text next to the textbox if they enter the wrong text.

I am wondering if there is a way to trigger a dialog box (e.g., alert('You must enter a value between 5 and 15')) if they enter an invalid number in the field.  The reason being, we've had a number of people who go through past that field quickly, and don't notice the red error text.  The alert() dialog, which will interrupt user activity and give an audion alert, will (hopefully) cut down on some of the errors.

I only want it to trigger when  they've entered invalid text.  So, I need to register a custom script block (really, just a one line "alert()" statement) if the client side validation is fired and fails.

How do I do that?  I know there must be a way...



9/26/2006 8:42:00 PM
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you can use the validation summary's "ShowMessageBox" attribute, like this:  

<asp:ValidationSummary ID="vs" ShowMessageBox="true" />

9/26/2006 11:13:12 PM

But I want it to show them the alert as soon as they move off the text box (if they've entered an invalid date).  This won't work until they hit the submit button, I believe...

9/27/2006 12:32:20 PM

hi Jbeall,

you can do this by using Java script..

in Page_Load

txt1.Attributes.Add("onblur", "checktext();");

In HTML page script block

function checktext()


var Tbox1 = document.getElementById( 'txt1' );

if( Tbox1.value >15)   // change according to your reqs


alert('please enter ............... in range');

return false;



My Blog

"Don't be afraid to be wrong; otherwise you'll never be right."
9/27/2006 3:13:23 PM

Yes, this is in fact what I'm doing right now.

I was just hoping there was some way to make the JS fire only when my validator failed.  Conceptually, here's what I wanted to do:

<asp:TextBox runat='server' ID='LengthInFeet'/>
<asp:RangeValidator runat='server' ID='LengthRangeValidator' MinimumValue='2' MaximumValue='10' Type='Integer' OnClientValidationFailure='alert("Valid lengths are 2 through 10");' />

The last bit that I put in bold is made up -- you can't really do that.

But it's what I was hoping to do.  If I could do that, then all my validation logic would be right there in my <asp:RangeValidator>  tag.  As it is now, I've got logic in both the .aspx and the .aspx.cs file.

But perhaps that's just the way it has to be. 

9/27/2006 4:14:15 PM

Try this..  this function alert the user if he/she enters text length less than 2 charcters or more than 10 characters otherwise the function do nothing..

basically it is just a client side validation when the focus moves away from that textbox

function validate()



var txt1 = document.getElementById("txt1");

if(txt1.value.length < 10 || txt1.value.length >2 )  // checking the length of the string

return true;



alert("Please Enter a Valid Number?");

return false;




My Blog

"Don't be afraid to be wrong; otherwise you'll never be right."
9/27/2006 5:38:33 PM

Hi jb,

I am the author of a commercial validation solution, Professional Validation And More. I built my software because there are numerous limitations to the original validators that demand hacks, extra coding, or simply cannot be done. This is a classic case. Another which would get the users attention is to change the color of the textbox when there is an error. A third, which is supported in ASP.NET 2, is to set focus back to the field with the error. (Use the SetFocusOnError property.) A fourth is to blink the error message a few times. All of these are reasonable solutions, yet you have to work within the constraints of the tool you have selected.

I can see a hack being brewed in this thread. I've never considered a hack for this before, but I would imagine it involving these elements:

1. Attach code to the onchange event to be run after all validators do their work.

2. Look through the list of validators assigned to that textbox and see if their isValid property is false.

3. Create a string containing the error messages from those validators and call alert() with it.

If you use my solution, its a built in feature (just like most the things users have demanded of validation). Just set the PeterBlum.VAM.Globals.Page.ShowAlertOnChange property to true in Page_Load. (My code supports all of the ways to get the user's attention described above.)

--- Peter Blum
Creator of Peter's Data Entry Suite (formerly Professional Validation And More and Peter's Date Package) and Peter's Polling Package
9/27/2006 6:11:23 PM

Hi Peter,

Thanks for the feedback.  I'll definitely be keeping your control set in mind.  I've seen it before and they look pretty powerful.

This is a different topic, but since I seem to have managed to attract the attention of someone who really knows how controls work, and how to build custom controls, I was wondering if you can give any insight into this.  How do I get Visual Studio to recognize that I can have child elements of a custom control?  I have made a control called EnhancedDropDownList, and it has ListItems as children.  It compiles fine, pages load and run fine, but Visual Studio gives me an error for every <asp:ListItem> that I have as a child.  How do I get that error to go away?  The thread discussing it is here -- nobody seems to know how to fix it.  I thought you might?


9/28/2006 3:56:34 PM
OK, I've given an answer there.
--- Peter Blum
Creator of Peter's Data Entry Suite (formerly Professional Validation And More and Peter's Date Package) and Peter's Polling Package
9/28/2006 6:37:41 PM

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