When asp.net use LinkButton to do the login button, the carriage return fails to submit the solution __.net

LinkButton belongs to a label, you must obtain the focus before you can use $ ("#<%=this.lbtnlogin.clientid%>"). Click ();
WORKAROUND: Direct trigger LinkButton postback event javascript: __doPostBack (' Lbtnlogin ', ');

<asp:textbox id= "txtloginname" cssclass= "TXT" runat= "server" tabindex= "1" placeholder= "username" ></asp:textbox >

 <asp:textbox id= "txtpassword" cssclass= "TXT" textmode= "Password" runat= "Server" tabindex= "2" 
placeholder= "Password" ></asp:TextBox>

<asp:linkbutton id= "Lbtnlogin" validationgroup= "Login" runat= " Server "width=" 173 "height=" 
onclientclick= "return valid ()" onclick= "Lbtnlogin_click" > Login </asp: Linkbutton>

<script type= "Text/javascript" > function valid () {var loginname = $ ("#<%=this.txtloginname.c
            Lientid%> "). Val (). Replace (" username "," ");
            var Loginpassword = $ ("#<%=this.txtpassword.clientid%>"). Val (). replace ("password", ""); if (LoginName = = "" | | Loginpassword = = "") {if (LoginName = = "" && Loginpassword = "") {$ ("#<% =this.validmessage.clientid%> "). Text (" Enter your username and password. ")
                    ");
                $ ("#<%=this.txtloginname.clientid%>"). focus (); else if (LoginName = "") {$ ("#<%=this.validmessage.clientid%>"). Text ("Please fill in the username.")
                    "); $ ("#<%=this.validmessage.clientid%>"). Text ("Please enter a username and password.)
                "); else {$ ("#<%=this.validmessage.clientid%>"). Text ("Enter your password.
                    ");
                $ ("#<%=this.txtpassword.clientid%>"). focus (); } $ ("#<%=this.validsuMmary.
                ClientID%> "). Show ();
            return false;
            else {return true; } $ (function () {$ ("#<%=this.txtloginname.clientid%>"). KeyUp (function (event) {//select already Account password Login return event for KeyDown, prevent event conflict, commit login using KeyUp event var e = Events | | window.event | |
                Arguments.callee.caller.arguments[0]; if (e && e.keycode = 13) {//Login box, carriage return event var Loginpassword = $ ("#<%=this.txtpassword.clientid
                    %> "). Val (). replace (" password "," "); if (Loginpassword = = "") {$ ("#<%=this.txtpassword.clientid%>"). focus ();/Enter, the detection password is not filled, then fixed to the password
                    box return;
                        } if (valid ()) {//form validation passed, submit login javascript: __dopostback (' Lbtnlogin ', ');
                        LinkButton belongs to a label, you must obtain the focus before you can use $ ("#<%=this.lbtnlogin.clientid%>"). Click (); Solution: Direct Triggering LinKbutton the postback Event &nbsp}});
                $ ("#<%=this.txtpassword.clientid%>"). KeyUp (function (event) {//Select Existing account password login return event is KeyDown, prevent event conflict, commit login use KeyUp event var e = Event | | window.event | |
                Arguments.callee.caller.arguments[0]; if (e && e.keycode = 13) {//Password box, carriage return event if (valid ()) {//form validation through Javascrip
        T: __doPostBack (' Lbtnlogin ', ');//Commit login}}});
    }); </script>