Visual basic code for login form in MS Access - ms-access

Question

I have two fields, username and password, currently there are two users, my code only accepts the 1st user's username and password, but not the second user. Cant seem to figure out where i should make the changes. I get an error in ms access related to duplicate data entry.
Please tell me what i can do to change my code, currently my visual basic code logic is, if username and password are entered correctly then open a form
Private Sub LoginBtn_Click()
Set L = CurrentDb.OpenRecordset("Login")
'validation to check if the user entered the username in the username field
If IsNull(Me.txtUsername) Or Me.txtUsername = "" Then
MsgBox "You must enter a User Name.", vbOKOnly, "Required Data"
Me.txtUsername.SetFocus
Exit Sub
End If
'validation to check if the user entered the password in the password field
If IsNull(Me.strPassword) Or Me.strPassword = "" Then
MsgBox "You must enter a Password.", vbOKOnly, "Required Data"
Me.strPassword.SetFocus
Exit Sub
End If
'check to see if the password and username match
If (Me.txtUsername = L.[Username]) And (Me.strPassword = L.[Password]) Then
'Close Member login form and open the member form
DoCmd.OpenForm "Memberform"
Else
MsgBox "Password Invalid. Please try again.", vbOKOnly, "Invalid Entry!"
Me.strPassword.SetFocus
End If
End Sub

Answer 1

It looks like the problem is the last If block: you're opening the Login table (or query?) but you're only looking at the first record, instead of looping through all the records to check if there's a match.
So, you could fix this by changing it to loop through the records until you find a match (not recommended), or you could instead make a query whose criteria are the supplied username and password and see if any records are returned.
Way 1 - looping through records:
Private Sub LoginBtn_Click()
'validation to check if the user entered the username in the username field
If IsNull(Me.txtUserName) Or Me.txtUserName = "" Then
MsgBox "You must enter a User Name.", vbOKOnly, "Required Data"
Me.txtUserName.SetFocus
Exit Sub
End If
'validation to check if the user entered the password in the password field
If IsNull(Me.strPassword) Or Me.strPassword = "" Then
MsgBox "You must enter a Password.", vbOKOnly, "Required Data"
Me.strPassword.SetFocus
Exit Sub
End If
'check to see if the password and username match
Set L = CurrentDb.OpenRecordset("Login")
Dim found As Boolean
found = False
If L.BOF And L.EOF Then
MsgBox "There are no usernames or passwords in the database.", vbOKOnly, "No login info"
Exit Sub
Else
Do While Not L.EOF
If (Me.txtUserName = L.[UserName]) And (Me.strPassword = L.[Password]) Then
found = True
Exit Do
End If
L.MoveNext
Loop
End If
If L.EOF And Not found Then
' at the last record and did not find a match
MsgBox "Invalid username or password. Please try again.", vbOKOnly, "Invalid Entry!"
Me.strPassword.SetFocus
' clean up
L.Close
Set L = Nothing
Else
' we found a match; close Member login form and open the member form
' clean up
L.Close
Set L = Nothing
DoCmd.OpenForm "Memberform"
DoCmd.Close acForm, Me.Name
End If
End Sub
Way 2 - a query:
Private Sub LoginBtn_Click()
'validation to check if the user entered the username in the username field
If IsNull(Me.txtUsername) Or Me.txtUsername = "" Then
MsgBox "You must enter a User Name.", vbOKOnly, "Required Data"
Me.txtUsername.SetFocus
Exit Sub
End If
'validation to check if the user entered the password in the password field
If IsNull(Me.strPassword) Or Me.strPassword = "" Then
MsgBox "You must enter a Password.", vbOKOnly, "Required Data"
Me.strPassword.SetFocus
Exit Sub
End If
'check to see if the password and username match
' Using a QueryDef with parameters to avoid SQL injection
Dim qdf as DAO.QueryDef
Set qdf = CurrentDb.CreateQueryDef("","SELECT Username, Password FROM Login WHERE Username=[_uname] AND Password=[_pw]")
qdf.Parameters("_uname") = Me.txtUsername
qdf.Parameters("_pw") = Me.strPassword
Set L = qdf.OpenRecordset
If L.BOF And L.EOF Then
' no match
MsgBox "Invalid username or password. Please try again.", vbOKOnly, "Invalid Entry!"
Me.strPassword.SetFocus
' clean up
L.Close
Set L = Nothing
Else
' we found a match; close Member login form and open the member form
'clean up
L.Close
Set L = Nothing
DoCmd.OpenForm "Memberform"
DoCmd.Close acForm, Me.Name
End If
End Sub