如何在VB.NET Visual Studio 2022中修复连接字符串未初始化错误

我使用Visual Studio .NET Framework + VB.NET开发，连接MS Access（.accdb）数据库时，一周来始终无法解决「The ConnectionString property has not been initialized」错误。

Module1.vb代码： #

Imports System.Data.OleDb
Module Module1
    Public cn As New OleDbConnection
    Public cm As New OleDbCommand
    Public dr As OleDbDataReader
    Sub ConnectToDatabase()
        Try
            Dim startupPath As String = AppDomain.CurrentDomain.BaseDirectory
            Dim connectionString As String = $"Provider=Microsoft.JET.OLEDB.4.0;Data Source={startupPath}\OSA_Records.accdb"
            Using cn As New OleDbConnection(connectionString)
                cn.Open()
            End Using

        Catch ex As Exception
            Console.WriteLine("ConnectToDatabase Error: " & ex.ToString())
            MsgBox(ex.Message, vbCritical)
        End Try
    End Sub
End Module

frmMain.vb加载事件代码： #

Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ConnectToDatabase()
    LoadRecordsStudent()
    LoadRecordsViolation()
    LoadRecordsProgram()
    LoadRecordsSection()
    LoadRecordsAcademicYear()
    AutoSuggestStudent()
End Sub

我已经尝试过所有相关的YouTube视频教程，但问题依然存在，希望有人能帮忙修复。如果需要更多相关信息，请告知，非常感谢！

内容的提问来源于stack exchange，提问作者AeroSphinx