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 .
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
Related
I can anyone tell me whats wrong with my code? I am a complete novice here and this is the first time I have tried writing something in quite a while,
The below code should be updating two fields in an access database
Private Sub TestButton_Click(sender As Object, e As EventArgs) Handles TestButton.Click
'connects application to database
Dim ConnString As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\DatabasePath\database.accdb"
Dim SqlString As String = "update SaintStaff set [StaffHours]=[#CAHours],[RecordedTime]=[#Time] where [StaffName] = " & Label2.Text & ""
'updates record in SaintStaff table.
Using conn As New OleDbConnection(ConnString)
conn.Open()
Using cmd As New OleDbCommand(SqlString, conn)
cmd.CommandType = CommandType.Text
cmd.Parameters.AddWithValue("[#CAHours]", Label6.Text)
cmd.Parameters.AddWithValue("[#Time]", Label10.Text)
cmd.ExecuteNonQuery()
End Using
conn.Close()
End Using
End Sub
I am getting the following error
System.Data.OleDb.OleDbException: 'No value given for one or more required parameters.'
and its highlighting the cmd text on each line, I cant tell what I am doing wrong, can anyone help?
Thank you
This Question was answered by MatSnow and olivier-jacot-descombes in the comments, the correct code looks as follows
Private Sub TestButton_Click(sender As Object, e As EventArgs) Handles TestButton.Click
'connects application to database
Dim ConnString As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\DatabasePath\Database.accdb"
Dim SqlString As String = "update SaintStaff set StaffHours = #CAHours, RecordedTime = #Time where StaffName = #staffname "
'updates record in SaintStaff table.
Using conn As New OleDbConnection(ConnString)
conn.Open()
Using cmd As New OleDbCommand(SqlString, conn)
cmd.CommandType = CommandType.Text
cmd.Parameters.Add("#CAHours", OleDbType.VarChar).Value = Label6.Text
cmd.Parameters.Add("#Time", OleDbType.VarChar).Value = Label10.Text
cmd.Parameters.Add("#Staffname", OleDbType.VarChar).Value = Label2.Text
cmd.ExecuteNonQuery()
End Using
conn.Close()
End Using
End Sub
Hello I am trying to do an update query on my database however I end up with this error message
System.InvalidOperationException: 'Operation is not valid due to the current state of the object.'
Here is the code for my search query which I then use in the update
Private Function SearchData(Fname As String, ID As Int32) As DataTable
Dim dt As New DataTable
Dim ds As New DataSet
Dim ssql As String = "SELECT * FROM customers WHERE fname LIKE #Fname OR CustomerID = #ID"
Using con As New SQLiteConnection(ConStr),
cmd As New SQLiteCommand(ssql, con)
con.Open()
cmd.Parameters.Add("#Fname", DbType.String).Value = $"%{Fname}%"
cmd.Parameters.Add("#ID", DbType.Int32).Value = ID
dt.Load(cmd.ExecuteReader)
Dim da As New SQLiteDataAdapter(cmd)
da.Fill(ds, "customers")
dt = ds.Tables(0)
If dt.Rows.Count > 0 Then
ToTextbox(dt)
End If
End Using
Return dt
End Function
This is the ToTextBox function
Public Sub ToTextbox(ByVal newdt)
txtFName.Text = newdt.Rows(0)(1).ToString()
txtLName.Text = newdt.Rows(0)(2).ToString()
mtxtContactNumber.Text = newdt.rows(0)(3).ToString()
txtAddress.Text = newdt.rows(0)(4).ToString()
txtTown.Text = newdt.rows(0)(5).ToString()
txtPostCode.Text = newdt.rows(0)(6).ToString()
End Sub
And the update function
Public Function updateguest(FirstName As String, ID As Integer) As Integer
Dim Result As Integer
Dim usql As String = "UPDATE Customers SET fname = #fname WHERE CustomerID = #ID;"
Using con As New SQLiteConnection(ConStr),
cmd As New SQLiteCommand(usql, con)
con.Open()
cmd.Parameters.Add("#fname", DbType.String).Value = FirstName
cmd.Parameters.Add("#ID", DbType.Int32).Value = ID
con.Open()
Result = cmd.ExecuteNonQuery
con.Close()
End Using
Return Result
End Function
And the Update button
Private Sub IbtnUpdate_Click(sender As Object, e As EventArgs) Handles ibtnUpdate.Click
Try
Dim Result = updateguest(txtFName.Text, CInt(txtSearchID.Text))
If Result > 0 Then
MsgBox("New RECORD HAS BEEN UPDATED!")
Else
MsgBox("NO RECORD HAS BEEN UPDATDD!")
End If
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
I believe you update problems are solved in comments.
You still have too much stuff in your DataAccess code. Just return the DataTable and use it in the user interface code.
Private Function SearchData(Fname As String, ID As Int32) As DataTable
Dim dt As New DataTable
Dim ssql As String = "SELECT * FROM customers WHERE fname LIKE #Fname OR CustomerID = #ID"
Using con As New SQLiteConnection(ConStr),
cmd As New SQLiteCommand(ssql, con)
con.Open()
cmd.Parameters.Add("#Fname", DbType.String).Value = $"%{Fname}%"
cmd.Parameters.Add("#ID", DbType.Int32).Value = ID
dt.Load(cmd.ExecuteReader)
End Using
Return dt
End Function
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim dt = SearchData(FirstNameTextBox.Text, CInt(IDTextBox.Text))
If dt.Rows.Count > 0 Then
ToTextbox(dt)
End If
End Sub
Public Sub ToTextbox(ByVal newdt As DataTable)
txtFName.Text = newdt.Rows(0)(1).ToString()
txtLName.Text = newdt.Rows(0)(2).ToString()
mtxtContactNumber.Text = newdt.Rows(0)(3).ToString()
txtAddress.Text = newdt.Rows(0)(4).ToString()
txtTown.Text = newdt.Rows(0)(5).ToString()
txtPostCode.Text = newdt.Rows(0)(6).ToString()
End Sub
I'm making a search bar using SELECT query and I want to transfer the results to a DataGridView. But I always get an empty DataGridView.
Nothing is wrong with the query, I already tried to input it manually in access. What am I doing wrong in the code? Here it is:
Using conn = New OleDbConnection(connstring)
Try
Dim Sql As String = "SELECT * FROM Products WHERE [Product Name] LIKE '" & txtSearchProduct.Text & "*'"
Dim da As New OleDbDataAdapter(Sql, conn)
Dim ds As New DataSet
da.Fill(ds)
DataGridView2.DataSource = ds.Tables(0)
Catch ex As Exception
MsgBox(ex.ToString, MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "Error")
End Try
End Using
The issue is as I stated in the comment. ADO.Net uses the % for the like to maintain consistency with most major Sql engines. But I would like to point out that your query is unsafe and subject to SQL injection so I have included an example of your code using a parameter to pass user input to the command.
Also note that the OleDbDataAdapter can be declared in a Using statement the same way you did with the OleDbConnection Note that you may however have to widen the scope of the dataset (ds) if you plan on doing other things with it.
Using conn As OleDbConnection = New OleDbConnection(connstring)
Try
Dim Sql As String = "SELECT * FROM Products WHERE [Product Name] LIKE #Product"
Using da As OleDbDataAdapter = New OleDbDataAdapter(Sql, conn)
da.SelectCommand.Parameters.Add("#Product", OleDbType.Varchar).Value = txtSearchProduct.Text & "%"
Dim ds As New DataSet
da.Fill(ds)
DataGridView2.DataSource = ds.Tables(0)
End Using
Catch ex As Exception
MsgBox(ex.ToString, MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "Error")
End Try
End Using
Like Charles has mentioned its always better to use parameters. My answer is a bit different whereas it uses a reader and not an adapter, and a datatable and not an entire dataset. An adapter should only be used if you intend to write back to the table, or typical scenarios include binding procedures. A DataSet is typically used when you have multiple tables and have a need to relate them. Also note, you most likely want a preceding % in your parameter if you want to match the string regardless of the position in the search column.
Try
Using conn = New OleDbConnection("YourConnString")
conn.Open()
Dim Cmd As New OleDbCommand("SELECT * FROM Products WHERE [Product Name] LIKE #Product", conn)
Cmd.Parameters.AddWithValue("#Product", "'%" & txtSearchProduct.Text & "%'")
Dim ProductsRDR As OleDbDataReader = Cmd.ExecuteReader
Dim DTable As New DataTable With {.TableName = "Products"}
DTable.Load(ProductsRDR)
DataGridView1.DataSource = DTable
conn.Close()
End Using
Catch ex As Exception
MsgBox(ex.ToString, MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "Error")
End Try
All you have to do is replacing the * sign with % in your Sql string, just like this:
This is your wrong Sql string:
Dim Sql As String = "SELECT * FROM Products WHERE [Product Name] LIKE '" & txtSearchProduct.Text & "*'"
Change it to this:
Dim Sql As String = "SELECT * FROM Products WHERE [Product Name] LIKE '" & txtSearchProduct.Text & "%'"
This should cover most of the common scenarios out there.
Imports System.Data.SqlClient
Public Class Form1
Dim sCommand As SqlCommand
Dim sAdapter As SqlDataAdapter
Dim sBuilder As SqlCommandBuilder
Dim sDs As DataSet
Dim sTable As DataTable
Private Sub load_btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles load_btn.Click
Dim connectionString As String = "Data Source=.;Initial Catalog=pubs;Integrated Security=True"
Dim sql As String = "SELECT * FROM Stores"
Dim connection As New SqlConnection(connectionString)
connection.Open()
sCommand = New SqlCommand(sql, connection)
sAdapter = New SqlDataAdapter(sCommand)
sBuilder = New SqlCommandBuilder(sAdapter)
sDs = New DataSet()
sAdapter.Fill(sDs, "Stores")
sTable = sDs.Tables("Stores")
connection.Close()
DataGridView1.DataSource = sDs.Tables("Stores")
DataGridView1.ReadOnly = True
save_btn.Enabled = False
DataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect
End Sub
Private Sub new_btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles new_btn.Click
DataGridView1.[ReadOnly] = False
save_btn.Enabled = True
new_btn.Enabled = False
delete_btn.Enabled = False
End Sub
Private Sub delete_btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles delete_btn.Click
If MessageBox.Show("Do you want to delete this row ?", "Delete", MessageBoxButtons.YesNo) = DialogResult.Yes Then
DataGridView1.Rows.RemoveAt(DataGridView1.SelectedRows(0).Index)
sAdapter.Update(sTable)
End If
End Sub
Private Sub save_btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles save_btn.Click
sAdapter.Update(sTable)
DataGridView1.[ReadOnly] = True
save_btn.Enabled = False
new_btn.Enabled = True
delete_btn.Enabled = True
End Sub
End Class
One time when I run this code it run smoothly but then when i search for names there is no record appears. Badly need your help guys for our program project. thanks in advance :)
This is my code :
Private Sub search_btn_Click(sender As Object, e As EventArgs) Handles search_btn.Click
Me.Show()
Search_Record()
End Sub
Private Sub Search_Record()
Dim conn As New OleDbConnection
Dim cmd As New OleDbCommand
Dim da As New OleDbDataAdapter
Dim dt As New DataTable
Dim sSQL As String = String.Empty
Try
conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\VB\HSU\HSU\G11B.mdb"
conn.Open()
cmd.Connection = conn
cmd.CommandType = CommandType.Text
sSQL = "SELECT Last_Name, First_Name FROM 10ABM"
sSQL = sSQL & "WHERE Last_Name like '%" & Me.search_txt.Text & "%'"
cmd.CommandText = sSQL
da.SelectCommand = cmd
da.Fill(dt)
Me.DataGridView1.DataSource = dt
If dt.Rows.Count = 0 Then
MsgBox("No record found!")
End If
Catch ex As Exception
MsgBox(ErrorToString)
Finally
conn.Close()
End Try
End Sub
Here is a code that retrieve values from the database, but my problem is that it throws out an exception saying "InvalidCastException was unhandled specified cast is not valid". I am now confused what went wrong, The code and the table stated below.
Here is the code:
Public connstring As String = "Provider=Microsoft.ACE.OLEDB.12.0; Data Source =" & Application.StartupPath &
"\TestData.accdb; Persist Security info = false"
Public Conn As New OleDbConnection
Private Sub TestForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Loard
Conn.ConnectionString = connstring
Conn.Open()
LoadValue( )
End Sub
Private Sub LoadValue( )
Dim i As Integer
Dim cmd As OleDbCommand = New OleDbCommand
With cmd
.CommandText = "SELECT MAX(Guard_ID) FROM Guard"
.CommandType = CommandType.Text
.Connection = Conn
.ExecuteNonQuery()
Dim reader As OleDbDataReader = cmd.ExecuteReader
If reader.Read Then
TextBox1.Text = reader.GetString(0)
i = TextBox1.Text + 1
TextBox1.Text = i
reader.Close()
End If
End With
End Sub
The table reference:
Exception Error:
I am really confused now on why the code does not work, any help and advice will be gladly accepted. Thanks in advance.
try this,
Private Sub LoadValue()
Dim i As Integer
Dim cmd As OleDbCommand = New OleDbCommand
With cmd
.CommandText = "SELECT MAX(Guard_ID) FROM Guard"
.CommandType = CommandType.Text
.Connection = Conn
.ExecuteNonQuery()
Dim reader As OleDbDataReader = cmd.ExecuteReader
If reader.Read Then
Dim tmpVal As Object = reader.Item(0)
TextBox1.Text = IIf(IsDBNull(tmpVal), "0", tmpVal.ToString())
i = CInt(TextBox1.Text) + 1
TextBox1.Text = i.ToString()
reader.Close()
End If
End With
End Sub