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();");

Answer 1

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..