Allow and Prevent postback in javascript in asp.net

Question

I was trying to validate dates using java script on button click event.If validation returns false post-back should be prevented and if returns true post-back should be allowed.

The problem is that post-back is occuring even if the validation returns false.....

I'm new to javascript.Kindly give me any solution.....

Here's my code

<script type="text/javascript">
    function ValidateDate() {

        var GridView = document.getElementById('GridView1');           
        var i = 1;
        var rows = GridView.rows.length;           
        for (var j = 0; j < rows - 2; j++) {
            i = i + 1;              
            var FromDate = new Date(document.getElementById('GridView1_ctl0' + i + '_txtFrom').value);
            var ToDate = new Date(document.getElementById('GridView1_ctl0' + i + '_txtTo').value);
            if (ToDate < FromDate) {
                document.getElementById('GridView1_ctl0' + i + '_txtFrom').focus();
                alert('ToDate is less than from date');
                return false;
            }
        }
        return true;      
    }
</script>

I've called javascript on pageload event

this.btnSave.Attributes.Add("onClick", "ValidateDate();");

try "onclick". It's the correct way to specify the attribute, even if it may work with the capital C. — jamesmortensen
– jamesmortensen, Commented Apr 7, 2012 at 8:25

Vishal Suthar · Accepted Answer · 2012-04-07 09:28:35Z

2

You forgot to specify return

You should try with:

this.btnSave.Attributes.Add("onClick", "return ValidateDate();");

You are returning the value back from the ValidateDate() so for such a condition you need to specify this at the time of function call, and when it returns false then it stops the execution further..

edited Apr 7, 2012 at 9:28

answered Apr 7, 2012 at 8:26

Vishal Suthar

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2 Comments

ksg Over a year ago

thank u for the correct answer..Can u explain how is it working ??

Vishal Suthar Over a year ago

I appended the explanation..@ksg

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