object reference not set to an instance of an object Inserting database sql array - vb.net

Question

How can i insert array textbox in database?I have to save each newboxes in access and it should be in different row..It has an error object reference not set to an instance of an object when saving the data
Public Class Form1
Dim boxes As New List(Of TextBox)
Dim combo As New List(Of ComboBox)
Private Sub Addbuttons(buttonCount As Integer)
Dim newbox As TextBox Dim newcombo As ComboBox
For i As Integer = 1 To buttonCount
newbox = New TextBox
newbox.Size = New Drawing.Size(575, 35)
newbox.Location = New Drawing.Point(10, 10 + 35 * (i - 1))
newbox.Name = "TextBox" & i
newbox.Text = newbox.Name
'connect it to a handler, save a reference to the array and add it to the form controls
boxes.Add(newbox)
Me.Controls.Add(newbox)
Next For i As Integer = 1 To buttonCount
newcombo = New ComboBox
newcombo.Size = New Drawing.Size(57, 20)
newcombo.Location = New Drawing.Point(864, 531 + 70 * (i - 1))
combo.Add(newcombo)
Me.Controls.Add(newcombo)
Next
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Addbuttons(Val(TextBox1.Text))
End Sub
Private Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
addbuyer()
End Sub
Private Sub addbuyer()
Dim newbox As TextBox
Try
datab = " Insert INTO sample (sample1,sample2) values ( '" & newbox.Text & "','" & newqty.Text & "')"
connDB()
cmd = New OleDbCommand(datab, conn)
Dim i As Integer
i = cmd.ExecuteNonQuery
If i > 0 Then
' MsgBox("Added SUccesfully", MsgBoxStyle.Information, "Confirmation")
Else
MsgBox("Failed Adding", MsgBoxStyle.Information, "Alert!")
End If
Catch ex As Exception
MsgBox(ex.Message)
Finally
cmd.Dispose()
conn.Close()
End Try
End Sub
End Class

Answer 1

In addbuyer, Dim newbox As TextBox is nothing and that's the cause of the error.
You added all the textbox controls to boxes so you need to loop thru that when you insert into the DB. One way to do it is by looping and passing each textbox by reference:
Private Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
For Each t As TextBox In boxes
addbuyer(t)
Next
End Sub
Private Sub addbuyer(ByRef newbox As TextBox)
Try
datab = " Insert INTO sample (sample1) values ( '" & newbox.Text & "')"
connDB()
cmd = New OleDbCommand(datab, conn)
Dim i As Integer
i = cmd.ExecuteNonQuery
If i > 0 Then
MsgBox("Added SUccesfully", MsgBoxStyle.Information, "Confirmation")
Else
MsgBox("Failed Adding", MsgBoxStyle.Information, "Alert!")
End If
Catch ex As Exception
MsgBox(ex.Message)
Finally
cmd.Dispose()
conn.Close()
End Try
End Sub