GridView with checkboxes

Hello members,

              I have used "Check box" inside the gridview...

              I need,

                           If i select the header check box , It should select all the checkbox inside the gridview...

              I have searched in google for this coding ...I got  lot of codes but couldn't get the correct code...

              I request anyone please provide me the correct code(using Javascript) thanks...

I have checkBoxes in my Gridview templete columns called "Category A" and "Category B". I want Select-All functionality, i.e. when the user checks the Select-All check Box in category A column, all the checkboxes must get checked under that column. Same for Category B.  I am trying with the code below. The problem with my code is, it selects all the check boxes in the entire gridview, "Category A" as well as "Category B"s checkboxes.  But, I want only checkboxes selected under the same column.

function SelectAllCheckboxesA(chk) {
                $('#<%=gvSurveys.ClientID %>').find("input:checkbox").each(function() {
                    if (this != chk) {
                        if ($(this).hasClass('CatA') != false) {
                            this.checked = chk.checked;
                        }
                    }
                    else {
                        alert($(this))
                    }
                });
            }

<asp:GridView ID="gvSurveys" runat="server" AutoGenerateColumns="false" AllowSorting="True" Width="1500px">
                           <Columns>
                              <asp:TemplateField>
                                 <HeaderTemplate>Category A    <asp:CheckBox ID="chkSelectAllCatA" runat="server" Visible="false" onclick="javascript:SelectAllCheckbox