Delete From Table error - sql

Question

i'm trying to create a delete button to delete a record ....
here's my code:
Dim SqlQuery As String = "DELETE FROM MyTable WHERE InvoiceNumber = " & id & ";"
'id is public shared as integer , which is ListView1.SelectedItems(0).Text
Dim SqlCommand As New OleDb.OleDbCommand
With SqlCommand
.CommandText = SqlQuery
.Connection = conn
.ExecuteNonQuery()
End With
I get an exception in .ExecuteNonQuery(), the error is
"ExecuteNonQuery() requires the command to have a transaction" ,
"Validate transaction" , "ExecuteReaderInternal"
assume that the database is connected, got info and delete button is button3 .
Also i will show you my whole form code:
Public Class Report
Public id As Integer
Public conn As New OleDb.OleDbConnection
Public connstring As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Ramy\Documents\Beach.accdb"
Private Property RivieraDataSet As Object
Private Sub Report_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
conn.Close()
End Sub
Private Sub Report_Load(sender As Object, e As EventArgs) Handles MyBase.Load
If conn.State = ConnectionState.Closed Then
Try
conn.ConnectionString = connstring
conn.Open()
MsgBox("DataBase opened successfully!", MsgBoxStyle.Exclamation)
loadlistview()
Catch ex As Exception
MsgBox(ex.ToString, MsgBoxStyle.Critical)
End Try
Else
MsgBox("DataBase Error!!", MsgBoxStyle.Critical)
End If
Dim reading As OleDb.OleDbDataReader
Dim cmd As New OleDb.OleDbCommand
Dim trans As OleDb.OleDbTransaction
trans = conn.BeginTransaction
cmd.CommandText = "SELECT * FROM MyTable"
cmd.Connection = conn
cmd.Transaction = trans
reading = cmd.ExecuteReader
Dim i
Do While reading.Read
i = Val(reading.Item("Total")) + i
Loop
TextBox7.Text = i
TextBox7.Text = Convert.ToDecimal(TextBox7.Text).ToString("N2") & " L.E"
End Sub
Sub loadlistview()
ListView1.FullRowSelect = True
ListView1.MultiSelect = False
ListView1.View = View.Details
ListView1.Columns.Clear()
ListView1.Items.Clear()
ListView1.Columns.Add("No", 30, HorizontalAlignment.Left)
ListView1.Columns.Add("InvoiceDate", 125, HorizontalAlignment.Left)
ListView1.Columns.Add("PersonsNumber", 70, HorizontalAlignment.Left)
ListView1.Columns.Add("PersonPrice", 80, HorizontalAlignment.Left)
ListView1.Columns.Add("CashierName", 100, HorizontalAlignment.Left)
ListView1.Columns.Add("Total", 100, HorizontalAlignment.Left)
Dim SqlQuery As String = "SELECT * FROM MyTable"
Dim SqlCommand As New OleDb.OleDbCommand
Dim SqlAdapter As New OleDb.OleDbDataAdapter
Dim table As New DataTable
With SqlCommand
.CommandText = SqlQuery
.Connection = conn
End With
With SqlAdapter
.SelectCommand = SqlCommand
.Fill(table)
End With
For i = 0 To table.Rows.Count - 1
With ListView1
.Items.Add(table.Rows(i)("InvoiceNumber"))
With .Items(.Items.Count - 1).SubItems
.Add(table.Rows(i)("InvoiceDate"))
.Add(table.Rows(i)("PersonsNumber"))
.Add(table.Rows(i)("PersonPrice"))
.Add(table.Rows(i)("CashierName"))
.Add(table.Rows(i)("Total"))
End With
End With
Next
End Sub
Private Sub ListView1_MouseClick(sender As Object, e As MouseEventArgs) Handles ListView1.MouseClick
Dim SqlQuery As String = "SELECT * FROM MyTable"
Dim SqlCommand As New OleDb.OleDbCommand
Dim SqlAdapter As New OleDb.OleDbDataAdapter
Dim table As New DataTable
With SqlCommand
.CommandText = SqlQuery
.Connection = conn
End With
With SqlAdapter
.SelectCommand = SqlCommand
End With
If ListView1.SelectedItems.Count > 0 Then
id = ListView1.SelectedItems(0).Text
TextBox1.Text = id
TextBox6.Text = ListView1.SelectedItems(0).SubItems(1).Text
TextBox3.Text = ListView1.SelectedItems(0).SubItems(2).Text
TextBox4.Text = ListView1.SelectedItems(0).SubItems(3).Text
TextBox2.Text = ListView1.SelectedItems(0).SubItems(4).Text
TextBox5.Text = ListView1.SelectedItems(0).SubItems(5).Text
End If
End Sub
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
Dim SqlQuery As String = "DELETE FROM MyTable WHERE InvoiceNumber = " & id & ";"
'id is public shared as integer , which is ListView1.SelectedItems(0).Text
Dim SqlCommand As New OleDb.OleDbCommand
With SqlCommand
.CommandText = SqlQuery
.Connection = conn
.ExecuteNonQuery()
End With
End Sub
End Class
I was searching for a mistake in my delete btn code for hours , but i can see everything is good..... but .ExecuteNonQuery() is so annoying .

Answer 1

In your Form_Load you open a transaction for your GLOBAL connection.
This means that every command executed using that connection should be informed of this transaction (and you do it in the Form_Load event setting the Command.Transaction property).
But in other parts of your program, executing a command with that connection and not setting the Transaction property will raise the mentioned error.
Looking at your code above I would suggest to remove altogether the Transaction because, as is, you don't need it.
Simply remove these lines in Form_Load
Dim trans As OleDb.OleDbTransaction
trans = conn.BeginTransaction
...
cmd.Transaction = trans
Instead, if for motives not apparent from the code above, you insist in keeping the Transaction then you should create the command from the connection so the transaction is passed to the command.
Dim SqlQuery As String = "DELETE FROM MyTable WHERE InvoiceNumber = " & id & ";"
Dim SqlCommand = conn.CreateCommand()
With SqlCommand
....
End With
By the way, I really suggest you to remove that global connection variable. It is only a source of problems (check if open, transactions etc...) Just make a function that creates it for you and use it in a Using Statement whenever you need it
Public Function GetConnection() As OleDb.OleDbConnection
Dim conn = New OleDb.OleDbConnection(connstring)
conn.Open()
return conn
End Function
And use it with Using Statement that close and dispose the enclosed object also in case of exceptions
Using conn = GetConnection()
Using command = conn.CreateCommand()
With command
command.CommandText = "DELETE FROM MyTable WHERE InvoiceNumber = " & id & ";"
command.ExecuteNonQuery()
End With
End Using
End Using
Pay also attention at possible sql injection scenarios. In your situation (reading an integer from a ListView) there are few problems, but a parameterized query is always better