i am currently getting this error, System.InvalidOperationException: 'Fill: SelectCommand.Conne-CodePudding

Imports System.Data
Imports System.Data.OleDb
Imports System.Data.DataTable

Public Class Form1

Private Sub btnlogin_Click(sender As Object, e As EventArgs) Handles btnlogin.Click
    Dim conn As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Katlego\Documents\LoginDb.accdb")
    Dim cmd As New OleDbCommand("select * from logintable where username1=@username1 and password1=@password1, conn")
    cmd.Parameters.Add("@username1", oleDbType:=OleDbType.VarChar).Value = txtusername.Text
    cmd.Parameters.Add("@password1", oleDbType:=OleDbType.VarChar).Value = txtpassword.Text
    Dim adapter1 As New OleDbDataAdapter(cmd)
    Using logintable As New DataTable
        Dim unused = adapter1.Fill(logintable)
        If logintable.Rows.Count <= 0 Then
            MsgBox("error username or password")
        Else
            MsgBox("login sucessfull")
        End If
    End Using
End Sub

CodePudding user response：

You need to open the connection first

conn.Open()

CodePudding user response：

There's a typo when you are initializing cmd object. You include the conn object inside the connection string. So the cmd object is missing a connection object.

Dim cmd As New OleDbCommand("select * from logintable where username1=@username1 and password1=@password1, conn")

Should be:

Dim cmd As New OleDbCommand("select * from logintable where username1=@username1 and password1=@password1", conn)