VB.net Check datatable for an existing account number

[Papa_Don]

Hi group,

I'm attempting to write code to check to see if an existing account number exists. The user is to input a 10 digit account number. The code then is to query the database to see if that number exists. If it does, the message box displays the message that the number exists. However the code I've written isn't working as I wish. Can you offer some suggestions as to how to do this correctly?

Here's what I've attempted:

Private Sub tbxAccountNo_TextChanged(sender As Object, e As EventArgs) Handles tbxAccountNo.TextChanged
    If GlobalVariables.custpnl1 = 2 And tbxAccountNo.Text.Length = 10 And IsNumeric(tbxAccountNo.Text) = True Then
        Dim dt As New DataTable()
        Dim rowIndex As Integer = 0
        Dim searchID As Int64
        Dim strQ As String = String.Empty
        Dim conStr As String

        Dim msgAcctNo As String

        strQ = "SELECT CUST_ACCT_NO
                FROM CUSTREC 
                WHERE CUST_ACCT_NO = " & searchID
        conStr = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\Don\Documents\Visual Studio 2019\SalesForm\DWHRPT.mdf;Integrated Security=True"

        Dim dataAdapter As New SqlDataAdapter(strQ, conStr)
        dataAdapter.Fill(dt)
        dataAdapter.Dispose()

        For i As Integer = 0 To (dt.Rows.Count - 1)
            rowIndex = i
            If IsDBNull(dt.Rows(rowIndex)("CUST_ACCT_NO")) Then
                acctNoExists = False
            Else
                msgAcctNo = CStr(dt.Rows(rowIndex)("CUST_ACCT_NO"))
                acctNoExists = True
                MessageBox.Show("This account number exists.  Please enter a unique 10 digit account number.", "", MessageBoxButtons.OK)
                Exit Sub
            End If
        Next
    End If
End Sub

The "Text_Changed" event is used to fire this off - when there are 10 numeric characters in the textbox. That part seems to be working correctly as I've toggled it to stop at "For i As Integer = 0 To (dt.Rows.Count - 1)". But at this point, that's the only thing that seems to be working.

If you can teach me what I'm doing wrong, please feel free to do so.

As always, thanks for your help.

Don

[Papa_Don]

I was able to figure this out. Here's what I did:

 Private Sub tbxAccountNo_LostFocus(sender As Object, e As EventArgs) Handles tbxAccountNo.LostFocus
    If GlobalVariables.custpnl1 = 2 And tbxAccountNo.Text.Length = 10 And IsNumeric(tbxAccountNo.Text) = True Then
        Dim dt As New DataTable()
        Dim rowIndex As Integer = 0
        Dim searchID As Int64 = Convert.ToInt64(tbxAccountNo.Text)
        Dim strQ As String = String.Empty
        Dim conStr As String

        strQ = "SELECT CUST_ACCT_NO
                FROM CUSTREC 
                WHERE CUST_ACCT_NO = " & searchID
        conStr = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\Don\Documents\Visual Studio 2019\SalesForm\DWHRPT.mdf;Integrated Security=True"

        Dim dataAdapter As New SqlDataAdapter(strQ, conStr)
        dataAdapter.Fill(dt)
        dataAdapter.Dispose()
        acctNoExists = False
        For i As Integer = 0 To (dt.Rows.Count - 1)
            rowIndex = i
            If searchID = Convert.ToInt64(CStr(dt.Rows(rowIndex)("CUST_ACCT_NO"))) Then
                acctNoExists = True
                MessageBox.Show("Account #" & searchID & " exists.  Please enter a unique 10 digit account number.", "", MessageBoxButtons.OK)
                tbxAccountNo.Clear()
                tbxAccountNo.Select()
                Exit Sub
            End If
        Next
    End If
End Sub

I hope someone else can use this method.

Don

[xrjf]

I imagine you are aware of SQL injection. If not you may read here about it.