Security authentication and web.config configuration of asp.net

asp.net|web| Security (1) in Web.config configuration
Modify options in <system.web>
The validation mode is set to form and the validation page is
<authentication mode= "Forms" >
<forms loginurl= "Login.aspx"/>
</authentication>
Do not allow anonymous users
<authorization>
<deny users= "?"/>
</authorization>

After </system.web> add a page that does not validate to use the database to access the database on the page to see if the user exists.
<location path= "Reg.aspx" >
<system.web>
<authorization>
<allow users= "*"/>
</authorization>
</system.web>
</location>

(2) in the code in the normal way, such as asking the other party to enter information to find the database or XML validation, after verification, the execution of this sentence will be validated by the same jump will begin to enter the page
System.Web.Security.FormsAuthentication.RedirectFromLoginPage (username,true);
Cancellation with System.Web.Security.FormsAuthentication.SignOut ();
If you do not want to jump back, you can first authorize and redirect to other pages System.Web.Security.FormsAuthentication.SetAuthCookie ();