FormsAuthentication.RedirectFromLoginPage not working

-->I get authenticaion error "unkown user"
Is that your custom error message or system generated?
Can you post the code you use for authentication and web.config.

HI guru sami

It is standard web.config stuff for membership.

It actually fails on this login code

 var user = UserService.GetUserByUsername(username.Text);

It works fine on my local pc and dev server BUT it does not work on the dev server if it returns null.

So if I put in wrong username it works fine locally but for some reason it errors saying unkown user on dev server

HI Yes

It is using custom membership provider that inherits from standard membership.

Username exists in database but I was testing for null user, ie, putting in wrong username

So if I put in wrong username on local PC it works fine handling null value returned but on dev server looking at the SAME database I get the same exepected behaviour unkown user but it throws an authentication exception "unkown user"

So I think my question is why is  that if I can return NULL to

var user = UserService.GetUserByUsername(username.Text);

which works fine on my local PC

but if I return NULL to

var user = UserService.GetUserByUsername(username.Text);

I get unhandled exception "Uknown user"  - on the dev server it cannot seem to handle having a null passed to         var user =

hmmm nothing else poping up ... can you try returning an empty string or empty object from GetUserByUsername instead of null if user is not found and see what the code does?

Forgive my ignorance but is the function GetUserByUsername not expecting a valid/existing username?