Here is a javascript code to select and deselect checkboxes placed in gridview:
<script language=”javascript” type=”text/javascript”>var counter = 0;
var pattern = ‘^ctl00_c1_gvvotes’;
// Get the checkboxes inside the Gridview which is part of the template column
function GetChildCheckBoxCount() {
var checkBoxCount = 0; var elements = document.getElementsByTagName(“INPUT”); for(i=0; i<elements.length;i++) {
if(IsCheckBox(elements[i]) && IsMatch(elements[i].id)) checkBoxCount++; }
return parseInt(checkBoxCount); }
// A function that checks if the checkboxes are the one inside the GridView
function IsMatch(id) {
var regularExpresssion = new RegExp(pattern); if(id.match(regularExpresssion)) return true; else return false;}
function IsCheckBox(chk) {
if(chk.type == ‘checkbox’) return true; else return false;}
function AttachListener(){
var elements = document.getElementsByTagName(“INPUT”); for(i=0; i< elements.length; i++) {
if( IsCheckBox(elements[i]) && IsMatch(elements[i].id)) {
AddEvent(elements[i],‘click’,CheckChild); }
}
}
function CheckChild(e) {
var evt = e || window.event; var obj = evt.target || evt.srcElement if(obj.checked){
if(counter < GetChildCheckBoxCount()) { counter++; }
}
else {
if(counter > 0) { counter–; } }
if(counter == GetChildCheckBoxCount()) { document.getElementById(“chkAll”).checked = true; }
else if(counter < GetChildCheckBoxCount()) { document.getElementById(“chkAll”).checked = false; } }
function AddEvent(obj, evType, fn) {
if (obj.addEventListener){
obj.addEventListener(evType, fn, true);return true;}
else if (obj.attachEvent){
var r = obj.attachEvent(“on”+evType, fn);return r;}
else
{
return false;}
}
function Check(parentChk) {
var elements = document.getElementsByTagName(“INPUT”); for(i=0; i<elements.length;i++) {
if(parentChk.checked == true) {
if( IsCheckBox(elements[i]) && IsMatch(elements[i].id)) {
elements[i].checked = true; }
}
else {
elements[i].checked = false; // reset the counter
counter = 0;
}
}
if(parentChk.checked == true) {
counter = GetChildCheckBoxCount();
}
}
</script>
gridview code:
<asp:TemplateField>
<HeaderTemplate>
<input type=”checkbox” id=”chkAll” name=”chkAll” onclick=”Check(this)” />
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID=”chkSelect” runat=”server” />
</ItemTemplate>
</asp:TemplateField>
Note: call javascript function in pages’ onload() event
