Question

I’m really new to ASP.net and I am currently trying to create a registration page on a site. I was successful in adding a user to the database but I decided to add another feature into the code to check what userID’s were available. For example, if a user deleted their account their userID would become available for use again. I’m trying to find the min value and the max value and add or subtract 1 depending on whether it is min or max. I can run the code I have written for this with no errors but the user is not added to the database. Can anyone help me figure out what I’m missing from my code to do this?

EDIT >>>>>
Code adds a user to database but it adds the new user at -1 instead. I don’t seem to be able to see where the issue is.

If (aDataReader2.Read() = False) Then
  aConnection1 = New OleDbConnection(aConnectionString)
  aConnection1.Open()
  aQuery = "Insert Into UserDetails "
  aQuery = aQuery & "Values ('" & userID & "','" & userFName & "','" & userLName & "','" & userEmail & "','" & userUsername & "','" & userPassword & "')"
  aCommand = New OleDbCommand(aQuery, aConnection1)
  aCommand.ExecuteNonQuery()
  aConnection1.Close()
ElseIf (min = 1) Then
  aConnection2 = New OleDbConnection(aConnectionString)
  aConnection2.Open()
  aCommand = New OleDbCommand(aQuery3, aConnection2)
  aDataReader2 = aCommand.ExecuteReader()
  userID = max + 1
  aQuery = "Insert Into UserDetails "
  aQuery = aQuery & "Values ('" & userID & "','" & userFName & "','" & userLName & "','" & userEmail & "','" & userUsername & "','" & userPassword & "')"
  aCommand = New OleDbCommand(aQuery, aConnection2)
  aCommand.ExecuteNonQuery()
  aConnection2.Close()
Else
  aConnection3 = New OleDbConnection(aConnectionString)
  aConnection3.Open()
  aCommand = New OleDbCommand(aQuery2, aConnection3)
  aDataReader2 = aCommand.ExecuteReader
  userID = min - 1
  aQuery = "Insert Into UserDetails "
  aQuery = aQuery & "Values ('" & userID & "','" & userFName & "','" & userLName & "','" & userEmail & "','" & userUsername & "','" & userPassword & "')"
  aCommand = New OleDbCommand(aQuery, aConnection3)
  aCommand.ExecuteNonQuery()
  aConnection3.Close()
  lblResults.Text = "User Account successfully created"
  btnCreateUser.Enabled = False
End If

Here’s the code I used to get the max and min values from the database. I’m getting a value of 0 for both of them – when min should be 1 and max should be 5

 Dim minID As Integer
 Dim maxID As Integer
 aQuery2 = "Select Min(UserID) AS '" & [minID] & "' From UserDetails"
 aQuery3 = "Select Max(UserID) AS ' " & [maxID] & "' From UserDetails"

Answer 1

It’s hard to say what
t the problem is exactly, since we see only a part of it. Where do min and max come from?

I cannot give you a solution, however, I suggest you to structure your code better. You have a lot (!) of redundant code. This makes the code difficult to read, to understand, to change and to test.

Put the user data into a class. This makes it easier to handle than a lot of individual variables.

Public Class User
    Public Property ID As Integer
    Public Property FirstName As String
    Public Property LastName As String
    Public Property EMail As String
    Public Property Username As String
    Public Property Password As String
End Class

Extract redundant code into subroutines

Private Sub CreateUser(ByVal u As User)
    Const InsertQuery As String = _
        "INSERT INTO UserDetails VALUES ({0},'{1}','{2}','{3}','{4}','{5}')"

    Dim query As String = String.Format(InsertQuery, u.ID, u.FirstName, u.LastName, _
                                                     u.Email, u.Username, u.Password)
    Using conn As New OleDbConnection(aConnectionString)
        conn.Open()
        Dim cmd As New OleDbCommand(query, conn)
        cmd.ExecuteNonQuery()
    End Using
End Sub

The code then becomes something like this

If Not aDataReader2.Read() Then
    CreateUser(user)
ElseIf min = 1 Then
    ...
    user.userID = max + 1
    CreateUser(user)
Else
    ...
    user.userID = min - 1
    CreateUser(user)
    lblResults.Text = "User Account successfully created"
    btnCreateUser.Enabled = False
End If

This looks much nicer now.

(My code is not tested, it’s just to give you an idea.)

---

UPDATE

You cannot read the min and max values like this. Try something like this

Dim min, max As Integer

Using conn As New OleDbConnection(aConnectionString)
    Dim cmd As OleDbCommand = _
        New OleDbCommand("SELECT MIN(UserID), MAX(UserID) FROM UserDetails", conn)
    conn.Open()
    Using reader As OleDbDataReader = cmd.ExecuteReader()
        reader.Read()
        If reader.IsDBNull(0) Then
            ' The table is empty
            min = 1
            max = 1
        Else
            min = reader.GetInt32(0)
            max = reader.GetInt32(1)
        End If
    End Using
End Using