Passing a variables in C# - windows

Question

I am trying to pass a variable that identifies a staff member from their login details to the next screen to populate the Tester ID box.
Would I be better using a global variable that is then read when the next screen is set up or would I be better to put it into a variable and send it to the next screen?
The login code sits as follows:
public Login()
{
InitializeComponent();
}
private void LoginButton_Click(object sender, EventArgs e)
{
String Username1 = StaffUsername.Text;
String Password1 = StaffPassword.Text;
String HardUser = "Test";
String HardPass = "Merlin123";
if (Username1 == "" && Password1 == "")
{
MessageBox.Show("Please Enter Login Id and Password");
}
else
{
if (Username1.Equals(HardUser) && Password1.Equals(HardPass))
{
this.Hide();
AddingClients M1 = new AddingClients();
M1.Show();
}
else{
this.Hide();
Login Lg = new Login();
Lg.Show();
MessageBox.Show("Incorrect Username or Password Entered");
}
}
}
}
}
I am using a hardcoded username and password for now, but in the actual program, I would have this call on a database and compare the username and the password and then go through to the next screen.
Would lit be better to have a global variable that the login action throws over to the next screen or would it be easier having a variable that the next screen reads and then populates the text box required? How would I go about this?
Thanks

Answer 1

The way you do this is to use the Thread.CurrentPrincipal.
Once the user is confirmed to be who they say they are, you can do:
private static void SignUserIn(string userName)
{
GenericIdentity identity = new GenericIdentity(userName, null);
Thread.CurrentPrincipal = new GenericPrincipal(identity);
}
Then whenever you need the userName, you use Thread.CurrentPrincipal.Identity.Name.
To extend this a little further, its probably best to abstract this a little bit, so you can swap in and out providers e.g. you might want to use Windows Authentication.
So you could do it like this:
public interface IAuthenticator
{
bool IsValidUser ( string username, string password );
IPrincipal SignInUser ( string username );
void SignOutCurrentUser();
}
public class DbAuthenticator : IAuthenticator
{
public bool IsValidUser ( string username, string password )
{
// Check user here and return bool if valid
}
public void SignInUser(string userName, string[] roles = null)
{
GenericIdentity identity = new GenericIdentity(userName, roles);
Thread.CurrentPrincipal = new GenericPrincipal(identity);
return Thread.CurrentPrincipal;
}
public void SignOutUser()
{
Thread.CurrentPrincipal = WindowsPrincipal.GetCurrent();
}
}
Then in your code, inject the authenticator using some sort of DI pattern. So MEF would be like this:
[Export(typeof(IAuthenticator))]
public interface IAuthenticator { }
And in your form:
[Import]
internal IAuthenticator authenticator;
private static void SignUserIn(string userName)
{
authenticator.SignUserIn(username);
}

Answer 2

You should have a User object and pass it to other pages and functions. That way they become more testable.
But you also need to store the object somewhere globally so you can retrieve the currently logged in user when needed. The problem with that is that piece of code then depends on that user storage existing/working, but if it's only one place it's okay.
PS: your title should be: pass the user on or store globally?