Register Form Issues VB.Net - vb.net

Question

I am having an issue when I am setting up this Register form.
My current code is this:
Public Class Form2
Dim con As New OleDb.OleDbConnection
Dim dbProvider As String
Dim dbSource As String
Dim MyDocumentsFolder As String
Dim TheDatabase As String
Dim FullDatabasePath As String
Dim ds As New DataSet
Dim da As OleDb.OleDbDataAdapter
Dim sql As String
Dim DBTest1 As String
Dim DBTestP1 As String
Dim cmd As New OleDbCommand(sql, con)
Dim connStr As String
Public Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim connection As New OleDb.OleDbConnection(connStr)
dbProvider = "Provider=Microsoft.ACE.OLEDB.12.0;"
TheDatabase = "\Robocopy_Test.accdb"
MyDocumentsFolder = "C:\Users\Dan\Desktop\WindowsApplication2"
FullDatabasePath = MyDocumentsFolder & TheDatabase
dbSource = "Data Source = C:\Users\Dan\Desktop\WindowsApplication2\Robocopy_Testaccdb1.accdb"
con.ConnectionString = dbProvider & dbSource
con.Open()
sql = "SELECT * FROM Robocopy"
da = New OleDb.OleDbDataAdapter(sql, con)
'da.Fill(ds, "Robocopy")
MessageBox.Show("Databse is Open")
DBTest1 = DBTest.Text
DBTestP1 = DBTestP.Text
'DBTest.Text = ds.Tables("Robocopy").Rows(0).Item(1)
'DBTestP.Text = ds.Tables("Robocopy").Rows(0).Item(2
sql = "INSERT INTO Robocopy(username,password) VALUES('" & DBTest1 & "','" & DBTestP1 & "')"
cmd.Connection = connection
connection.Open()
cmd.CommandText = sql
da.InsertCommand = cmd
da.InsertCommand.ExecuteNonQuery()
connection.Close()
'With cmd.Parameters
'.AddWithValue("usernamer", DBTest.Text)
'.AddWithValue("password", DBTestP.Text)
'.AddWithValue("email", txtsub.text)
'.AddWithValue("contactnum", txtau.text)
'End With
'cmd.ExecuteNonQuery()
End Sub
Public Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
con.Close()
MessageBox.Show("Database Is now Closed")
End Sub
End Class
I am having the issue at connection.open(). The error that I am having is
The ConnectionString property has not been initialized.
I have been trying for the past hour to find different ways to write to the database but to no prevail and I cannot figure this out.
[In response to Steve
My code after editing and still the same error
Imports System.Data.OleDb
Public Class Form2
Dim connection As New OleDb.OleDbConnection
Dim dbProvider As String
Dim dbSource As String
Dim MyDocumentsFolder As String
Dim TheDatabase As String
Dim FullDatabasePath As String
Dim ds As New DataSet
Dim da As OleDb.OleDbDataAdapter
Dim sql As String
Dim DBTest1 As String
Dim DBTestP1 As String
Dim cmd As New OleDbCommand(sql, connection)
Dim connStr As String
Public Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim connection As New OleDb.OleDbConnection(connStr)
dbProvider = "Provider=Microsoft.ACE.OLEDB.12.0;"
TheDatabase = "\Robocopy_Test.accdb"
MyDocumentsFolder = "C:\Users\Dan\Desktop\WindowsApplication2"
FullDatabasePath = MyDocumentsFolder & TheDatabase
dbSource = "Data Source = C:\Users\Dan\Desktop\WindowsApplication2\Robocopy_Testaccdb1.accdb"
Me.connection.ConnectionString = dbProvider & dbSource
Me.connection.Open()
sql = "SELECT * FROM Robocopy"
da = New OleDb.OleDbDataAdapter(sql, connection)
'da.Fill(ds, "Robocopy")
MessageBox.Show("Databse is Open")
DBTest1 = DBTest.Text
DBTestP1 = DBTestP.Text
'DBTest.Text = ds.Tables("Robocopy").Rows(0).Item(1)
'DBTestP.Text = ds.Tables("Robocopy").Rows(0).Item(2
sql = "INSERT INTO Robocopy(username,password) VALUES('" & DBTest1 & "','" & DBTestP1 & "')"
cmd.Connection = connection
connection.Open()
cmd.CommandText = sql
da.InsertCommand = cmd
da.InsertCommand.ExecuteNonQuery()
connection.Close()
'With cmd.Parameters
'.AddWithValue("usernamer", DBTest.Text)
'.AddWithValue("password", DBTestP.Text)
'.AddWithValue("email", txtsub.text)
'.AddWithValue("contactnum", txtau.text)
'End With
'cmd.ExecuteNonQuery()
End Sub
Public Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
connection.Close()
MessageBox.Show("Database Is now Closed")
End Sub
End Class

Answer 1

Global variables could be very ....evil. Expecially if you name them with the same name of a local variable.
Me.connection is not the same variable connection declared as local variable inside the sub. You set the connection string on the global variable then use the local variable without any connection string
Change these two lines
Me.connection.ConnectionString = dbProvider & dbSource
Me.connection.Open()
removing the Me.
connection.ConnectionString = dbProvider & dbSource
connection.Open()
and don't open the connection two times.
In any case, you don't need the adapter at all to execute an insert command
Public Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
dbProvider = "Provider=Microsoft.ACE.OLEDB.12.0;"
dbSource = "Data Source = C:\Users\Dan\Desktop\WindowsApplication2\Robocopy_Testaccdb1.accdb"
Dim connStr = dbProvider & dbSource
DBTest1 = DBTest.Text
DBTestP1 = DBTestP.Text
sql = "INSERT INTO Robocopy(username,[password]) VALUES('" & DBTest1 & "','" & DBTestP1 & "')"
Using connection = New OleDb.OleDbConnection(connStr)
Using cmd = new OleDb.OleDbCommand(sql, connection )
connection.Open()
cmd.ExecuteNonQuery()
'With cmd.Parameters
'.AddWithValue("usernamer", DBTest.Text)
'.AddWithValue("password", DBTestP.Text)
'.AddWithValue("email", txtsub.text)
'.AddWithValue("contactnum", txtau.text)
'End With
'cmd.ExecuteNonQuery()
End Using
End Using
End Sub
I see also that you have commented out the Parameterized approach to your query. Please do yourself a favour and restore as soon as possible the parameters logic. It is a lot more safe and avoids numerous errors
Finally Password is a reserved keyword in Access.Use square brakets around it otherwise you will see an unexplicable "Syntax Error" in your insert command