how to make a datagridview cellvaluechange 2 column which trigged loop - vb.net

Question

I am developing a sales order application. I am using a datagridview to fill the sales order.
the field in my datagridview are as per below
ItemCode - ItemDescription - qty - price
The description field is a combobox.
What I want is that when a user input an ItemCode, it automatically check my database and give me the Itemdescription
I also want user to be able to select an item from the ItemDescription which is a combobox, and it wil automatically update my Itemcode.
Private Sub salesorder_dgv_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles salesorder_dgv.CellValueChanged
If salesorder_dgv.Rows.Count > 0 Then
If e.ColumnIndex = 0 Then
Dim READER As SqlDataReader
conn.Open()
Dim query As String
query = "select * from item where code = '" & salesorder_dgv.Rows(e.RowIndex).Cells(0).Value & "'"
cmd = New SqlCommand(query, conn)
READER = cmd.ExecuteReader
If READER.Read Then
salesorder_dgv.Rows(e.RowIndex).Cells(1).Value = READER.GetString(2)
End If
conn.Close()
End If
If e.ColumnIndex = 1 Then
Dim READER As SqlDataReader
conn.Open()
Dim query As String
query = "select * from item where description = '" & salesorder_dgv.Rows(e.RowIndex).Cells(1).Value & "'"
cmd = New SqlCommand(query, conn)
READER2 = cmd.ExecuteReader
If READER.Read Then
salesorder_dgv.Rows(e.RowIndex).Cells(0).Value = READER.GetString(1)
End If
conn.Close()
End If
End If
End Sub
Is there a way to make this code work? i am getting "The Connection was not closed"

Answer 1

There's a lot wrong there so I'll first address what you have to clean it up, then address how you should be doing it.
As suggested in the comments, you should be creating all your ADO.NET objects where you need them, including the connection. You create, use and destroy in the narrowest scope possible. Also, if you only want data from a single column, don't use SELECT *. Retrieve only the column(s) you need. As you're only retrieving data from one column of one row, you should be using ExecuteScalar rather than ExecuteReader.
Next, you should acquaint yourself with the DRY principle, i.e. Don't Repeat Yourself. You have two blocks of code there that are almost identical so you should extract out the common parts and write that only once and pass in the different parts.
Finally, don't use string concatenation to insert values into SQL code. ALWAYS use parameters. It avoids a number of issues, most importantly SQL injection, which is quite possible in your case, as the user is entering free text. With all that in mind, the code you have would be refactored like so:
Private Sub salesorder_dgv_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles salesorder_dgv.CellValueChanged
If salesorder_dgv.RowCount > 0 Then
Dim sourceColumnIndex = e.ColumnIndex
Dim targetColumnIndex As Integer
Dim query As String
Select Case sourceColumnIndex
Case 0
targetColumnIndex = 1
query = "SELECT description FROM item WHERE code = #param"
Case 1
targetColumnIndex = 0
query = "SELECT code FROM item WHERE description = #param"
Case Else
Return
End Select
Dim row = salesorder_dgv.Rows(e.RowIndex)
Dim sourceValue = row.Cells(sourceColumnIndex).Value
Using connection As New SqlConnection("connection string here"),
command As New SqlCommand(query, connection)
command.Parameters.AddWithValue("#param", sourceValue)
connection.Open()
row.Cells(targetColumnIndex).Value = command.ExecuteScalar()
End Using
End If
End Sub
Now to how you should have done it. If you're populating a combo box column with all the descriptions then you must be querying the database for them in the first place. What you should have done is retrieved both the descriptions and the codes in that initial query. That way, you never have to go back to the database. You can populate a DataTable with both the codes and the descriptions and then much of the work will be done for you.
For the example below, I started by setting up the form in the designer, which meant adding and configuring the appropriate columns in the grid and adding the BindingSource components. That also includes setting the DataPropertyName property of each grid column so it binds to the appropriate source column. I'm also manually populating the item data here but you would be getting that data from your database.
Private itemTable As New DataTable
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
LoadItemData()
LoadSaleData()
End Sub
Private Sub LoadItemData()
With itemTable.Columns
.Add("code", GetType(String))
.Add("description", GetType(String))
End With
With itemTable.Rows
.Add("123", "First Item")
.Add("abc", "Second Item")
.Add("789", "Third Item")
.Add("xyz", "Fourth Item")
.Add("01a", "Fifth Item")
End With
itemBindingSource.DataSource = itemTable
With itemDescriptionColumn
.DisplayMember = "Description"
.ValueMember = "Description"
.DataSource = itemBindingSource
End With
End Sub
Private Sub LoadSaleData()
Dim saleTable As New DataTable
With saleTable.Columns
.Add("ItemCode", GetType(String))
.Add("ItemDescription", GetType(String))
.Add("Quantity", GetType(Integer))
.Add("Price", GetType(Decimal))
End With
saleBindingSource.DataSource = saleTable
salesorder_dgv.DataSource = saleBindingSource
End Sub
Private Sub salesorder_dgv_CellValidating(sender As Object, e As DataGridViewCellValidatingEventArgs) Handles salesorder_dgv.CellValidating
If e.RowIndex >= 0 AndAlso
e.ColumnIndex = 0 AndAlso
Not String.IsNullOrEmpty(e.FormattedValue) Then
'Check that the code entered by the user exists.
e.Cancel = (itemBindingSource.Find("code", e.FormattedValue) = -1)
If e.Cancel Then
MessageBox.Show("No such item")
End If
End If
End Sub
Private Sub salesorder_dgv_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles salesorder_dgv.CellValueChanged
Dim rowIndex = e.RowIndex
Dim sourceColumnIndex = e.ColumnIndex
If rowIndex >= 0 And sourceColumnIndex >= 0 Then
Dim sourceColumnName As String
Dim targetColumnName As String
Dim targetColumnIndex As Integer
Select Case sourceColumnIndex
Case 0
sourceColumnName = "code"
targetColumnName = "description"
targetColumnIndex = 1
Case 1
sourceColumnName = "description"
targetColumnName = "code"
targetColumnIndex = 0
Case Else
Return
End Select
Dim itemRow = itemBindingSource(itemBindingSource.Find(sourceColumnName, salesorder_dgv(sourceColumnIndex, rowIndex).Value))
Dim code = CStr(itemRow(targetColumnName))
salesorder_dgv(targetColumnIndex, rowIndex).Value = code
End If
End Sub
You start by populating the items and binding that data to the combo box column and then create an empty DataTable for the sales and bind that to the grid. The code checks that any manually entered codes actually do match items and it will set the description when a code is entered manually and the code when a description is selected from the list. It does this by referring back to the BindingSource containing the item data each time, so no extra queries. You might want to consider retrieving the price data for each item too, and calculating the price for that row based on that and the quantity.