ms access 2010 and vs2010 how to connect - visual-studio-2010

Question

Program crash in cmd.ExecuteNonQuery() row
Public Class Form1
Dim conn As New OleDb.OleDbConnection
Private Sub RefreshData()
If Not conn.State = ConnectionState.Open Then
'open connection
conn.Open()
End If
Dim da As New OleDb.OleDbDataAdapter("SELECT Oznaka as [Oznaka], " & _
"ReN as [ReN], RmN " & _
" FROM Tabela ORDER BY Oznaka", conn)
Dim dt As New DataTable
'fill data to datatable
da.Fill(dt)
'offer data in data table into datagridview
Me.DataGridView1.DataSource = dt
'close connection
conn.Close()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim cmd As New OleDb.OleDbCommand
If Not conn.State = ConnectionState.Open Then
'open connection if it is not yet open
conn.Open()
End If
cmd.Connection = conn
'check whether add new or update
If Me.txtOznaka.Tag & "" = "" Then
'add new
'add data to table
cmd.CommandText = "INSERT INTO Tabela(Oznaka, ReN, RmN) " & _
" VALUES('" & Me.txtOznaka.Text & "','" & Me.txtReN.Text & "','" & _
Me.txtRmN.Text & "'')"
cmd.ExecuteNonQuery()
Else
'update data in table
cmd.CommandText = "UPDATE Tabela " & _
" SET Oznaka=" & Me.txtOznaka.Text & _
", ReN='" & Me.txtReN.Text & "'" & _
", RmN='" & Me.txtRmN.Text & "'" & _
" WHERE Oznaka=" & Me.txtOznaka.Tag
cmd.ExecuteNonQuery()
End If
'refresh data in list
RefreshData()
'clear form
'Me.btnClear.PerformClick()
'close connection
conn.Close()
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
conn = New OleDb.OleDbConnection
conn.ConnectionString = "Provider=Microsoft.Jet.Oledb.4.0; Data Source=" & Application.StartupPath & "\baza.mdb"
'
'get data into list
Me.RefreshData()
End Sub
End Class

Answer 1

Are you running the INSERT or the UPDATE query when it crashes?
If it's the INSERT query, it's probably because the SQL string has one ' too much at the end:
... Me.txtRmN.Text & "'')"
^
here!
If it's the UPDATE query: if Oznaka is a string column, put the value in quotes:
" SET Oznaka='" & Me.txtOznaka.Text & "'" & _
instead of
" SET Oznaka=" & Me.txtOznaka.Text & _
An even better solution for both of these issues would be: use SQL parameters in your queries instead of concatenating strings.
Here are some examples to get started:
INSERT with transaction and parameters?
Pass a NULL in a parameter to a DateTime field in a stored procedure