[RESOLVED] Problems with datareader

Hello, :wave:

I´m trying to make a LOGIN BOX using a datareader and a table with 4 columns:

- chvpassword
- txtlogin
- txtpassword
- chvtipoutilizador (in portuguese: type of user)

but i get problems in this line:

VB Code:

Me.chvtipoutilizador = ler.Item(4)

the error message says: "Invalid attempt to read when no data is present"

but i got that column filled! I dont knows what happens!

the whole code:

VB Code:

Imports System.Data.SqlClient
Public Class Login
    Public chvtipoutilizador As Integer
 
    Private Sub tbEntrar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tbEntrar.Click
        login()
 
    End Sub
    Sub login()
 
 
        Dim textoconexao As String = "server=(local);database=orca2005;integrated security=true"
        Dim connection As New SqlConnection(textoconexao)
        Dim comandoSQL As New Data.SqlClient.SqlCommand
        Dim parametro As New SqlParameter
        comandoSQL.CommandType = Data.CommandType.Text
        comandoSQL.CommandText = "select * from tabPassword where txtlogin=@login and txtPassword=@Password"
        comandoSQL.Connection = connection
        Try
            connection.Open()
            parametro = comandoSQL.Parameters.Add("@login", Data.SqlDbType.NVarChar)
            parametro.Direction = Data.ParameterDirection.Input
            parametro.Value = Me.tbNome.Text
            parametro = comandoSQL.Parameters.Add("@Password", Data.SqlDbType.NVarChar)
            parametro.Direction = Data.ParameterDirection.Input
            parametro.Value = Me.tbPassword.Text
            If connection.State = Data.ConnectionState.Open Then
                Dim ler As SqlDataReader
                ler = comandoSQL.ExecuteReader
 
                If ler.HasRows Then
                    MessageBox.Show("Seja Bem-vindo!")
                    Me.chvtipoutilizador = ler.Item(4)
                    tipo()
 
                    Dim entrar As New principal
                    entrar.Show()
                    Me.Close()
                Else
                    MessageBox.Show("Erro de login!")
                    Me.tbNome.Clear()
                    Me.tbPassword.Clear()
 
                End If
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        Finally
            comandoSQL.Dispose()
            connection.Close()
        End Try
 
    End Sub
    Sub tipo()
        If chvtipoutilizador = 1 Then
            principal.labellog.Text = "Administrador"
        Else
            principal.labellog.Text = "Utilizador"
        End If
    End Sub
 
 
End Class

Are you sure as it starts at 0 so col 4 is actually 3?
Herses some code from one of my readers

VB Code:

Do While objDatabase.SqlRdrLKAgents.Read
                AgentName = objDatabase.SqlRdrLKAgents.GetString(0)

So it looks like your missing the Get part in yours.

Also

VB Code:

comandoSQL.CommandText = "select * from tabPassword where txtlogin=@login and txtPassword=@Password"

is very bad, if someone adds a new column in the database and your referencing in your apps by column number then your col references returned will go out of sync use the column names in your command text.

You have to .Read from your reader before retrieving values.

-tg

Usually you use a While loop to get data from a DataReader:

VB Code:

While myReader.Read()
    'Get values from current record here.
End While

The Read method advances to the next record and returns False when there are no records left. You must call it first to advance to the first record.

Quote:

---

Originally Posted by techgnome

You have to .Read from your reader before retrieving values.

-tg

---

And how i do that?

Like this:

Quote:

---

Originally Posted by jmcilhinney

Usually you use a While loop to get data from a DataReader:

VB Code:

While myReader.Read()
    'Get values from current record here.
End While

The Read method advances to the next record and returns False when there are no records left. You must call it first to advance to the first record.

---

-tg`

Now that's good advice, tg. :D