Checking if at least one checkbox has been checked

[uicouic]

Hi all. I need JavaScript to validate that atleast one checkbox has been checked in a form before the record(s) can be deleted.

- I have an <asp:button id="btnDelete"...> and the checkbox is created via grdData_ItemDataBound with id="chkRecordId":

Protected Sub grdData_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles grdData.ItemDataBound
 
        If e.Item.ItemType <> ListItemType.Header And e.Item.ItemType <> ListItemType.Footer   Then
            e.Item.Cells(1).Text = "<input type='checkbox' name='chkRecordId' value='" & e.Item.Cells(0).Text & "'/>"
 
       End If
End Sub

How do I achieve this? Any help would be greatly appreciated.

Thanks.

[acoder]

Since the checkboxes are named "chkRecordId", you can access them using :

var checkboxes = document.getElementsByName("chkRecordId");

then loop over them and check the checked property. If true, then the current checkbox (which you've reached in the loop) is checked otherwise not.

PS. please use [code] tags around your code. Thanks!

[uicouic]

@acoder
Ok I'll try it out. Thanks alot.

Sorry, I'll do it next time. New here :P

[uicouic]

By the way, can I just use:

if (checkboxes.checked==false) {
    strMessage += "<li>Please select minimum one competition category record  to delete<br>";
 

[acoder]

No, you can't. checkboxes would be an array, so you need to index it, e.g.
checkboxes[0] to refer to the first checkbox. You can use a for loop:

for (i = 0; i < checkboxes.length; i++) {
    if (!checkboxes[i].checked) ...
}

[uicouic]

Oh ok I get it now. Thanks alot acoder. Really appreciate it.
:)

[acoder]

No problem at all. You're welcome :)

[uicouic]

Bummer just when I thought I could get it to work, an error propped up:
"Object reference not set to an instance of an object."

These two lines caused the error:

strRecordIds = Request.Form("chkRecordId") 
'Use the Request.Form to collect data from checkboxes
 
aryRecordId = strRecordIds.Split(",") 
'Use the Split method to generate an Array, aryRecordId

Something to do with the aryRecordId I guess as it is split via strRecordIds as shown above.

Btw, as advised my code in the .aspx file is:

var checkboxes = document.getElementsByName("chkRecordId");
 
    for (int i = 0; i < checkboxes.length; i++) {
    if (checkboxes[i].checked != true) {
    strMessage += "<li>Please select minimum one competition category record to delete<br>";
    return false;
    }
    }
 

Please help, thanks.

[acoder]

Are you sure that's a JavaScript problem? Those two lines are not JavaScript code.

[uicouic]

Those two lines are found in the code-behind file of the webform where the checkboxes are found.(server-side)
Thus, I don't think it is a JavaScript problem. Must be a problem with the array of some sorts. (link between the code-behind file and .aspx JavaScript)

Hope I have provided adequate information.

[acoder]

In that case, you'll have better luck in the ASP.NET forum. Please ask there instead.

[uicouic]

Ok thanks again acoder :)

[acoder]

Just a note though before you go: your code

var checkboxes = document.getElementsByName("chkRecordId");
 
    for (int i = 0; i < checkboxes.length; i++) {
    if (checkboxes[i].checked != true) {
    strMessage += "<li>Please select minimum one competition category record to delete<br>";
    return false;
    }
    }
 

will not work as desired because it's checking that all checkboxes are checked instead of at least one checkbox which could be validated as follows:

for (int i = 0; i < checkboxes.length; i++) {
     if (checkboxes[i].checked) return true;
}
strMessage += "<li>Please select minimum one competition category record to delete<br>";
return false;