Help with instructions for a login system

I've been working with my last project from my 3 programming course, and right now I think I'm doing pretty well, basically all I gotta do is interact with Access tables, save, edit, create, etc...

That has been working out pretty well, but right now I'm stuck with my login system, I've created some methods where I encrypt the password, and then I send the password to a table called "security". The fields in the table are: username, password, email, type of account.

I can successfully insert all the respective data in it. Right now I am stuck with the validation. I need to create a system that will let me verify if the username exist (I did it successfully trying to insert the username again and if the username exists it will return an exception), but I don't know how to verify the password that is 开发者_开发百科in the same line.

I was wondering if there is any instruction with which I can extract the information of each field from the username that I verified? please help me... idk if I explain myself.. ?

ok thank your very much but do u know how can I retrieve it into a variable I have something like this "select contra from Seguridad where usuaruio = @CLAVE"

You are going to want o read a record from the table where the username field is the value of the user name to be tested. If no record found then insert the record. If a record found then do other things.

How to do this in VB.Net I don't know.

The query created in code would like something like

"SELECT * from UserTable where UserNameField = "' & varUserName & "'"