vb.net - VB.NET パブリック '追加' エラー

Question

私のコード:

    Imports System.Data.OleDb
Public Class DBase

    Dim conn As New OleDbConnection
    Dim myqry As String = Nothing
    Dim mycmd As New OleDbCommand
    Dim mydr As OleDbDataReader
    Dim str As String = Nothing
    Dim objCmd As New OleDb.OleDbCommand

    Private Sub DBase_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Call LVsettings()
        Call ConnToDB()
        Call FillListview()
        Call Set1()
    End Sub
#Region "FillListView"

    Sub FillListview()
        LV.Items.Clear()
        myqry = "SELECT * from Accounts ORDER BY YrandSec,FirstName Asc"
        mycmd = New OleDbCommand(myqry, conn)
        mydr = mycmd.ExecuteReader

        While mydr.Read
            With LV
                .Items.Add(mydr("Number"))
                With .Items(.Items.Count - 1).SubItems
                    .Add(mydr("StudNo"))
                    .Add(mydr("FirstName"))
                    .Add(mydr("LastName"))
                    .Add(mydr("YrandSec"))
                    .Add(mydr("Exer1")) - Error occurs here
                    .Add(mydr("Exer2"))
                    .Add(mydr("Exer3"))
                    .Add(mydr("Exer4"))
                    .Add(mydr("Exer5"))
                End With
            End With
        End While
    End Sub

#End Region

エラー：

ERROR - (Overload resolution failed because no Public 'Add' can be called with these arguments:
    'Public Function Add(text As String) As System.Windows.Forms.ListViewItem.ListViewSubItem':
        Argument matching parameter 'text' cannot convert from 'DBNull' to 'String'.
    'Public Function Add(item As System.Windows.Forms.ListViewItem.ListViewSubItem) As System.Windows.Forms.ListViewItem.ListViewSubItem':
        Argument matching parameter 'item' cannot convert from 'DBNull' to 'ListViewSubItem'.)