Bagaimana cara menghindari penyegaran halaman setelah acara klik tombol di asp.net

<asp:UpdatePanel ID="UpdatePanel1" runat="server">

    <ContentTemplate>

        <div style="margin-bottom: 20px; margin-top: 20px;"><span><strong style="font-size: large;">Edit User</strong></span></div>
        <div>
            <span style="float: left; width: 50%;"> </span> <span style="float: left; width: 50%;">
                <span style="width: 100%; float: left; text-align: right;">
                    <asp:Label ID="lblMessage" runat="server" Text="-"></asp:Label></span>
            </span>
        </div>

        <div style="width: 100%; float: left;">
            <hr />
        </div>

        <div style="width: 816px; margin-left: 5px; margin-top: 20px; height: 463px;">

            <div style="width: 100%; float: left; padding-top: 15px; height: 257px; margin-left: 0px;">
                <span class="Divide">
                    <span class="simDivide1">FullName</span>
                    <span class="simDivide">
                        <asp:TextBox ID="txtfullname" runat="server" Width="180px">
                        </asp:TextBox>
                    </span>

                </span>
                <span class="Divide">
                    <span class="simDivide1"></span>
                    <span class="simDivide"></span>
                </span>

                <span class="Divide">
                    <span class="simDivide1">Username</span>
                    <span class="simDivide">
                        <asp:TextBox ID="txtusername" runat="server" Width="180px">
                        </asp:TextBox>
                    </span>
                </span>

                <span class="Divide">
                    <span class="simDivide1"></span>
                    <span class="simDivide"></span>
                </span>

                <span class="Divide">
                    <span class="simDivide1">Password</span>
                    <span class="simDivide">
                        <asp:TextBox ID="txtpassword" runat="server" Width="180px">
                        </asp:TextBox>
                    </span>
                </span>

                <span class="Divide">
                    <span class="simDivide1"></span>
                    <span class="simDivide"></span>
                </span>

                <span class="Divide">
                    <span class="simDivide1">Mobile No
                    </span>
                     <span class="simDivide"><asp:TextBox ID="txtmobileno" runat="server" Width="180px">
                    </asp:TextBox>
                    </span>
                </span>

                <span class="Divide">

                    <span class="simDivide"></span>
                </span>

                <span class="Divide">
                    <span class="simDivide1">Role
                    </span>
                     <span class="simDivide"><asp:TextBox ID="txtrole" runat="server" Width="180px">
                    </asp:TextBox>
                    </span>
                </span>

                <script src="jquery-2.0.2.js"></script>

                <script language="javascript">

                    function done() {
                        var list = document.getElementById("tid");
                        list.removeChild(list.lastChild);

                    }

                    function changecourse(e) {

                        var change = document.getElementById('mytext').value;
                        var i = 1;

                        mNewObj = document.createElement('div');
                        mNewObj.id = "BOX" + i;
                        mNewObj.style.visibility = "show";
                        mNewObj.innerHTML = change + "&nbsp<a href='#' style='text-decoration: none; color:red' onClick='done()'> x </a> ";

                        document.getElementById("tid").appendChild(mNewObj);
                        i++
                        var a = document.getElementById('mytext').selectedIndex;
                        document.getElementById("ContentPlaceHolder1_Hidden1").value = a;
                        //document.getElementById("ContentPlaceHolder1_btninsert").click();

                        deleted();

                    }

                    function yes() {

                        $("#ContentPlaceHolder1_btninsert").click();

                    }

                    //function insert() {

                    //    $.ajax({
                    //        type: "POST",
                    //        url: "Edituser.aspx.cs/insert",

                    //        success: function () { alert('success'); },
                    //        error: function () { alert('error'); }

                    //    });

                    //}

                    function cancel() {

                        var select = document.getElementById('mytext');
                        select.remove(select.selectedIndex);
                    }

                    function deleted() {

                        document.getElementById("mytext").style.display = 'none';
                        document.getElementById("Button1").style.display = 'none';
                        document.getElementById("tid").style.display = 'inline';
                        document.getElementById("mylink").style.display = 'inline';
                    }

                    function showdiv() {

                        document.getElementById("mylink").style.display = 'none';
                        document.getElementById("mytext").style.display = 'inline';
                        document.getElementById("Button1").style.display = 'inline';

                    }

                </script>

            <input id="Hidden1" type="hidden" runat="server" />
            </div>
            <asp:Button ID="btnUpdate" runat="server" OnClick="btnUpdate_Click" Style="margin-left: 5px" Text="Edit" Width="39px" />
            <br>
            <br>

            <asp:UpdatePanel runat="server">
                <ContentTemplate>
           &nbsp&nbsp&nbsp&nbsp<div id="tid" >
                               </div>
            <div id="di">

                <a id="mylink" onclick="showdiv()">Add Depot</a>

                <select id='mytext' name='mytext' style="display: none">
                    <option>--Select--</option>
                    <option>Mumbai</option>
                    <option>Delhi</option>
                    <option>Banglore</option>
                    <option>Ahmedabad</option>
                </select>
               <input type="button" id="Button1" style="display: none" onclick=" changecourse(); yes(); cancel(); return false;" value="add" />
                </div>
            <asp:Button ID="btninsert" runat="server"  Style="display: none" OnClick="btninsert_Click" Text="Insert" ValidationGroup="C" />

                </ContentTemplate>
                </asp:UpdatePanel>
             </ContentTemplate>
</asp:UpdatePanel>

    protected void btninsert_Click(object sender, EventArgs e)
    {
        string a = Hidden1.Value;
        string UserId = Convert.ToString(Session["LoginId"]);
        con.Open();
        SqlCommand cmd = new SqlCommand("INSERT INTO UserDepot (UserId,DepotId)" +
            "VALUES ('" + UserId + "','" + a + "')", con);
        cmd.ExecuteNonQuery();
        con.Close();

    }