ExecuteNonQuery requires an open and available Connection. The connection's current state is closed. แก้ไงหรอคับมือใหม่เจอบัคงี้ งงกวนช่วยทีคับ

Private Sub FSave()
        'Try

        Conn = New OleDbConnection(strConnString)
        Conn.Open()
        Dim cmd As OleDbCommand = New OleDbCommand("Select * From TB_Book", Conn)
        Dim adp As OleDbDataAdapter = New OleDbDataAdapter(cmd)
        Dim dataset As DataSet = New DataSet
        Dim sql As String

        'Select Case flag
        'Case 0
        'Getmax()
        sql = "INSERT INTO [TB_Book](Book_Name,Book_Detail,Book_Cost,Book_Quantity,Book_Rent,Book_Publisher,Book_Date,Book_Penalty) Values('" & txtBook.Text & "','" & txtdetail.Text & "','" & txtPrice.Text & "','" & txtStock.Text & "','" & txtRent.Text & "','" & txtPub.Text & "','" & txtDate.Text & "','" & txtPenalty.Text & "')"
        cmd = New OleDbCommand(sql, Conn)
        cmd.ExecuteNonQuery()
        Conn.Close()

        Dim response As DialogResult = MessageBox.Show("บันทึกเสร็จสมบูรณ์", "บันทึกข้อมูล", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Cleartxt()
        FShow()


        'Case 1
        sql = "Update [TB_Book] Set Book_Name='" & txtBook.Text & "',Book_Detail='" & txtdetail.Text & "',Book_Cost='" & txtPrice.Text & "',Book_Quantity='" & txtStock.Text & "',Book_Rent='" & txtRent.Text & "',Book_Publisher='" & txtPub.Text & "',Book_Date='" & txtDate.Text & "',Book_Penalty='" & txtPenalty.Text & "' where Book_ID='" & txtcodebook.Text & "'"
        cmd = New OleDbCommand(sql, Conn)
        cmd.ExecuteNonQuery()
        Conn.Close()

        Dim result As DialogResult = MessageBox.Show("แก้ไขเสร็จสมบูรณ์", "แก้ไขข้อมูล", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Cleartxt()
        FShow()