Update ValidationSummary list on control blurs?

Question

A ValidationSummary will show a list of errors on postback. As each field is fixed, it's validator is fired, and any validation text will disappear. I want to automatically update the ValidationSummary as well.

The following works fine:

<asp:TextBox ID="ForenameTextBox" onblur="ValidationSummaryOnSubmit()" runat="server" />

but this isn't ideal, as it means changing and maintaining this on all fields. (ValidationSummaryOnSubmit is a Microsoft function.) So I tried to do it dynamically:

addEvent(window, "load", UpdateValidationSummary);

function addEvent(obj, evType, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(evType, fn, true);
    } else {
        if (obj.attachEvent) {
            var r = obj.attachEvent("on" + evType, fn);
            return r;
        }
    }
}

function removeEvent(obj, evType, fn) {
    if (obj.removeEventListener) {
        obj.removeEventListener(evType, fn, true);
        return true;
    } else if (obj.detachEvent) {
        var r = obj.detachEvent("on" + evType, fn);
        return r;
    }
}

function UpdateValidationSummary() {
    if (typeof (Page_Validators) == "undefined") {
        return;
    }
    var i, val, ctrl;
    for (i = 0; i < Page_Validators.length; i++) {
        val = Page_Validators[i];
        if (val.controltovalidate != null && val.controltovalidate != "") {
            ctrl = document.getElementById(val.controltovalidate);
            if (ctrl != null && typeof (ValidationSummaryOnSubmit) == "function") {
                //add call to ValidationSummary on blur
                addEvent(ctrl, "blur", ValidationSummaryOnSubmit);
            }
        }
    }
}

This doesn't work though - the whole ValidationSummary disappears when one field is fixed, and the ValidationSummaryOnSubmit function seems to get called twice. If I use a simple assignment instead of the addEvent function it works, but I want to cater for fields that might already have something going on in the onBlur event.

Basically I think I just need to add a call to the ValidationSummaryOnSubmit function to the "list" of onBlur handlers for each control. Why doesn't the code above seem to do this?

Menstruation

This is another approach you might find helpful; #9611439 – Contentious

Answer 1

Here's a server-side approach to get the onblur attribute on all TextBoxes (which should also work with Validation Groups):

• Create a class derived from TextBox, e.g., TextBoxEx
• Add the attribute in this derived class e.g., this.Attributes.Add("onblur", string.Format("ValidationSummaryOnSubmit('{0}')", this.ValidationGroup);
• Use tag mapping so that all of your existing <asp:TextBox> tags will still work: <system.web> <pages> <tagMapping> <add tagType="System.Web.UI.WebControls.TextBox" mappedTagType="MyControls.TextBoxEx"/> </tagMapping> </pages> </system.web>

Another way would be to use ControlAdapters to add the attribute.

Relevant links:
Understanding ASP.NET Validation
MSDN - tagMapping Element for pages

Unfaithful

yeah, that's a good idea, thanks. I would like to know why my script doesn't quite work though... – Menstruation

When I use the first method, simply putting it in the asp control's attributes, I also get the validation message appearing twice. Anyone know what's causing this? – Gangboard