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Hi, I got this error in my Immediate Window when I try to debug. I am trying to insert data into a table in Microsoft Access. Also it seems that I failed to connect to database. Here is the code that I have.

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
' Check if username or password is empty
If PasswordTextBox.Text = "" Or UsernameTextBox.Text = "" Then
MessageBox.Show("Please complete the required fields..", "Authentication Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
' Both fields was supply
' Check if user exist in database
' Connect to DB
Dim conn As New System.Data.OleDb.OleDbConnection()
conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\user1\Documents\PutLock.accdb"


Dim sql As String = "SELECT * FROM PutLockSignUp WHERE Username='" & UsernameTextBox.Text & "' AND Password = '" & PasswordTextBox.Text & "'"
Dim sqlCom As New System.Data.OleDb.OleDbCommand(sql, conn)

'Open Database Connection
sqlCom.Connection = conn

Dim sqlRead As System.Data.OleDb.OleDbDataReader = sqlCom.ExecuteReader()

If sqlRead.Read() Then

' If user enter wrong username and password combination
' Throw an error message
MessageBox.Show("Username and Password do not match..", "Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

'Clear all fields
PasswordTextBox.Text = ""
UsernameTextBox.Text = ""

'Focus on Username field
End If

Catch ex As Exception
MessageBox.Show("Failed to connect to Database..", "Database Connection Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

End If
End Sub

What I have tried:

I have tried searching for solution in google but I couldnt understand some of the explanation as I am still new in VB.NET. Btw, this is my school assignment. Please help me.
Updated 29-Jul-16 7:44am
Richard Deeming 29-Jul-16 12:55pm    
And you're currently throwing away all of the useful details from the exception that you've caught, and displaying a generic error message instead. Remove that handler, or log the exception somewhere, so that you can get to the root cause of the problem.

1 solution

There are several things very wrong here.
The first is that you should never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.
Concatenating strings as part of your login procedure is spectacularly dumb, as it lets anyone do what they want to your DB without even having a valid login. Or indeed bypassing your login completely...

The second is as bad: Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^] - it's in C# rather than VB, but it pretty simple to understand.

Fix them, and the problem you have noticed will probably go away at the same time...
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