Select all checkbox using javascript and save it in database

Please Help me out. To do this.I am Beginner in Asp.net C#
<asp: checkbox ID="Group1" runat="server">Select All<asp: checkbox>
<asp: checkbox runat="server">Item 1<asp: checkbox>
<asp: checkbox runat="server">Item 2<asp: checkbox>

<asp: checkbox ID="Group2" runat="server">Select All<asp: checkbox>
<asp: checkbox runat="server">Item 1<asp: checkbox>
<asp: checkbox runat="server">Item 2<asp: checkbox>