Friday, May 4, 2012

Check/uncheck CheckBox in a GridView using Javascript



I am going to present here a functionality that selects / deselects all checkboxes of a particular column inside a GridView control, provided the header checkbox of that column is checked or unchecked using JavaScript. This functionality also has a feature that when all checkboxes of a particular column inside the GridView are checked, then the header checkbox gets checked, and vice versa.

Using the code

I have used a TemplateField inside the GridView and put a CheckBox in the ItemTemplate as well as another CheckBox in the HeaderTemplate of the TemplateField.
The HTML code looks like this:
<asp:GridView ID="gvCheckboxes" runat="server" 
              AutoGenerateColumns="False" OnRowCreated="gvCheckboxes_RowCreated">
      <asp:BoundField HeaderText="S.N." DataField="sno">
         <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
         <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
      <asp:TemplateField HeaderText="Select">
            <asp:CheckBox ID="chkBxSelect" runat="server" />
         <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
         <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
            <asp:CheckBox ID="chkBxHeader" 
                 onclick="javascript:HeaderClick(this);" runat="server" />
            <asp:CheckBox ID="chkBx" runat="server" />
         <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
   <RowStyle BackColor="Moccasin" />
   <AlternatingRowStyle BackColor="NavajoWhite" />
   <HeaderStyle BackColor="DarkOrange" Font-Bold="true" ForeColor="white" />
Attach a client-side onclick event on the header checkbox [chkBxHeader].
<asp:CheckBox ID="chkBxHeader" onclick="javascript:HeaderClick(this);" runat="server" /> 
Put the following code in the GridView's RowCreated event:
if (e.Row.RowType == DataControlRowType.DataRow && 
   (e.Row.RowState == DataControlRowState.Normal ||
    e.Row.RowState == DataControlRowState.Alternate))
   CheckBox chkBxSelect = (CheckBox)e.Row.Cells[1].FindControl("chkBxSelect");
   CheckBox chkBxHeader = (CheckBox)this.gvCheckboxes.HeaderRow.FindControl("chkBxHeader");
   chkBxSelect.Attributes["onclick"] = string.Format
In the above code, a client side onclick event has been attached to the child checkbox [chkBxChild].
Add this JavaScript in the page’s head section:
<script type="text/javascript">
var TotalChkBx;
var Counter;

window.onload = function()
   //Get total no. of CheckBoxes in side the GridView.   TotalChkBx = parseInt('<%= this.gvCheckboxes.Rows.Count %>');

   //Get total no. of checked CheckBoxes in side the GridView.   Counter = 0;

function HeaderClick(CheckBox)
   //Get target base & child control.   var TargetBaseControl = 
       document.getElementById('<%= this.gvCheckboxes.ClientID %>');
   var TargetChildControl = "chkBxSelect";

   //Get all the control of the type INPUT in the base control.   var Inputs = TargetBaseControl.getElementsByTagName("input");

   //Checked/Unchecked all the checkBoxes in side the GridView.   for(var n = 0; n < Inputs.length; ++n)
      if(Inputs[n].type == 'checkbox' && 
                Inputs[n].id.indexOf(TargetChildControl,0) >= 0)
         Inputs[n].checked = CheckBox.checked;

   //Reset Counter   Counter = CheckBox.checked ? TotalChkBx : 0;

function ChildClick(CheckBox, HCheckBox)
   //get target control.   var HeaderCheckBox = document.getElementById(HCheckBox);

   //Modifiy Counter;    if(CheckBox.checked && Counter < TotalChkBx)
   else if(Counter > 0) 

   //Change state of the header CheckBox.   if(Counter < TotalChkBx)
      HeaderCheckBox.checked = false;
   else if(Counter == TotalChkBx)
      HeaderCheckBox.checked = true;
In the above script, there are two global variables: TotalChkBx and Counter. These are initialised in the window.onload event. There are two methods: HeaderClick and ChildClick. The method HeaderClick checks / unchecks all checkboxes of a particular column inside the GridView depending upon whether the header checkbox is checked or unchecked. The method ChildClick checks / unchecks the header checkbox depending upon whether all checkboxes of a particular column inside the GridView are checked or unchecked.
Just download the sample application and enjoy coding! I hope you will like this article

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