On a click of a button i should open one diallog form i am doing this in asp.net and jquery please do help me

On a click of a button i should open one diallog form i am doing this in asp.net and jquery please do help me

Below is my code
 <script type="text/javascript">
        $("#BtnMakeallotment")
      .button()
      .click(function () {
          $("#dialog-form").dialog("open");
      });

    </script>
    <form>
    <fieldset>
    <asp:GridView ID="GridAllotment" runat="server" AutoGenerateColumns="false"></asp:GridView>
    </fieldset>
    </form>

But i am not getting dialog form dont know what is the problem . Please help me