ascx:

<%

@ Control Language="C#" AutoEventWireup="true" CodeFile="EditBankerDetails.ascx.cs"

<div id="tabPersonal" class="divcontentinner">
 <table cellspacing="5" class="tablerow">
 <tr id="TR_FIRSTNAME">
 <td>
  <asp:Label runat="server"  ID="lblFIRSTNAME" Text="First Name:" />
 </td>
 <td >
     <asp:TextBox runat="server" ID="txtFIRSTNAME" CssClass="textbox" />
 </td>
 </tr>
 </table>
</div>

codebehind:
namespace SWB.Modules.SWBMasterData
{
    public partial class DesktopModules_SWBMasterData_EditBankerDetails : PortalModuleBase
    {

        #region Private Members
        protected int id = -1;
        protected string languageUI = "";
        ObjBankerForm gui = new ObjBankerForm();
        #endregion

        protected void Page_Load(object sender, System.EventArgs e)
        {
            try
            {
                if (!Page.IsPostBack)
                {
                    string homeURL = DotNetNuke.Common.Globals.NavigateURL();
                    string updateValue = "<script>";
                    updateValue += "function goToHome(){window.location.href =\'" + homeURL + "\';}";
                    updateValue += "</script>";
                    if (!Page.ClientScript.IsClientScriptBlockRegistered("UpdateValue"))
                        Page.ClientScript.RegisterClientScriptBlock(GetType(), "UpdateValue", updateValue);

                    //register the client scripts
                    if (!Page.ClientScript.IsClientScriptBlockRegistered("masterdata.js"))
                        Page.ClientScript.RegisterClientScriptInclude(GetType(), "masterdata.js", ModulePath + "Resources/masterdata.js");
                }
               
            }
            catch (Exception exc) //Module failed to load
            {
                Exceptions.ProcessModuleLoadException(this, exc);
            }
        }

        protected void btnSave_Click(object sender, System.EventArgs e)
        {
        Banker banker = new Banker();
        GetFieldValues(banker);
        ObjBankerForm gui = new ObjBankerForm();
        gui.updateBanker;
        }
       
        protected void GetFieldValues(Banker banker)
        {
          
            banker.FirstName = txtFIRSTNAME.Text;
            banker.LastName = txtLASTNAME.Text;
        }
  }
  }

thanks for answering, actually the problem was with the "AutoEventWireUp" . I set it to true and was doing page overload etc. Now I have solved it. thanks