changepassword without using changepassword control

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage2.master" AutoEventWireup="true" CodeFile="admin_changePwd.aspx.cs" Inherits="admin_changePwd" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
    <style type="text/css">
        .style1
        {
            width: 212px;
        }
        .style2
        {
            width: 387px;
        }
    </style>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<br />
<br />
<br />
    <table style="width: 100%;" align="center">
        <tr>
            <td class="style1">
                &nbsp;
            </td>
            <td class="style2">
                &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                User Name:<asp:TextBox ID="txtuser" runat="server"></asp:TextBox>
            </td>
            <td>
                &nbsp;
            </td>
        </tr>
        <tr>
            <td class="style1">
                &nbsp;
            </td>
            <td class="style2">
                &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                Old PassWord:<asp:TextBox ID="txtAminpwd" runat="server" TextMode="Password"
                    ontextchanged="txtAminpwd_TextChanged"></asp:TextBox>
            </td>
            <td>
                &nbsp;
            </td>
        </tr>
        <tr>
            <td class="style1">
                &nbsp;
            </td>
            <td class="style2">
                &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                New PassWord:<asp:TextBox ID="txtAminpwd1" runat="server" TextMode="Password"></asp:TextBox>
            </td>
            <td>
                &nbsp;
            </td>
        </tr>
        <tr>
            <td class="style1">
                &nbsp;
            </td>
            <td class="style2">
                Confirm PassWord:<asp:TextBox ID="txtadminpwd2" runat="server"
                    TextMode="Password"></asp:TextBox>
            </td>
            <td>
                &nbsp;
            </td>
        </tr>
        <tr>
            <td>
                &nbsp;
            </td>
            <td>
                 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                <asp:Button ID="btnad" runat="server" Text="Update" onclick="btnad_Click" />
            </td>
            <td>
                &nbsp;
            </td>
        </tr>
    </table>
</asp:Content>