Validation & remeber values of selected checkboxes in grid controls using javascript

This article explains how to make validation on checkboxes and remember the selected checkboxes' values in DataGrid/GridView etc, together. This will make xecution faster as we wont have to use FindControl method of grid controls.

I have always been in need of this and used this approach in almost every project.

//ASPX Code

<asp:GridView runat="server" AutoGenrateColumns="false">

<Columns>

<asp:TemplateField HeaderText="Select">

<ItemTemplate>

<input type="checkbox" id="chk_<%#Eval("id")%>" value="<%#Eval("id")%>" />

</ItemTemplate>

</asp:TemplateField>

...... (other column templates)

</Columns>

</asp:GridView>

//JavaScript code

function getCheckboxSelection()
{
    var strID="";
    for (i=0; i < document.forms[0].elements.length; i++)
    {
        if ((document.forms[0].elements[i].type == 'checkbox') && (document.forms[0].elements[i].id.indexOf(ObjID) > -1))
        {
            if (document.forms[0].elements[i].checked == true)
            strID += document.forms[0].elements[i].value+",";
        }
    }
    if(strID!="") strID = strID.substring(0,strID.length-1);
    return strID;
}

If strID is "" then we can display error saying that "no checkbox was selected" else we can store strID (comma separated values of selected checkboxes) in HiddenField on aspx page which will be accessed in code behind to performed some operations on these selected values.