Add a FBA User to a SharePoint Group Programatically

SPSecurity.RunWithElevatedPrivileges(delegate

                               {

                                   using (SPSite site = new SPSite(SPContext.Current.Web.Url))

                                   {

                                       using (SPWeb web = site.OpenWeb())

                                       {

                                           //adding user to the contributor group

                                           web.AllowUnsafeUpdates = true;

                                           //i:0#.f|sql-membershipprovider|chana

                                           string usernameWithProvider = "i:0#.f|sql-membershipprovider|" + usr.UserName;

                                          

                                           web.AllUsers.Add(usernameWithProvider, txtUserName.Text, txtUserName.Text, "");

                                           try

                                           {

                                               SPUser spuser = web.AllUsers[usernameWithProvider];

                                               if (spuser != null)

                                               {

                                                   SPGroup spGroup = web.Groups["Dev Members"];

                                                   if (spGroup != null)

                                                       spGroup.AddUser(spuser);

                                                   web.Update();

                                                   web.AllowUnsafeUpdates = false;

                                               }

                                           }

                                           catch { }

                                           web.Update();

                                           web.AllowUnsafeUpdates = false;

                                       }

                                   }

                               });