VB.netエラー 'Null例外が処理されず、列の引数がnullになりません'

Question

VB.netでツリービューを作成しようとしていますが、MSAccess 2010データベースからデータを読み込む必要があります。このプログラムを実行しようとすると、エラーが発生します。引数Null例外が処理されなかったため、 'column'引数はNULLになりませんプログラムがクラッシュします。ここでは、コードは次のとおりです。

Imports System.Data.OleDb 

Public Class frmRating 

Private Sub frmRating_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
    'Database Connections and Datasets 
    Dim DSRating As DataSet 
    Dim CNRating As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\BlockHeadDatabase.accdb;Persist Security Info=False;") 
    'DataAdapters to hold records 
    Dim DARatings As New OleDb.OleDbDataAdapter("SELECT Rating FROM Rating", CNRating) 
    Dim DATitle As New OleDb.OleDbDataAdapter("SELECT Title, Lending_Class FROM Title Order By Title", CNRating) 
    Dim DADVD As New OleDb.OleDbDataAdapter("SELECT DVD_NO, Branch_Code FROM DVD", CNRating) 

    'Instantiate the datasets, open the connection and fill the dataAdapters from the table 
    DSRating = New DataSet() 
    CNRating.Open() 

    DARatings.Fill(DSRating, "Rating") 
    DATitle.Fill(DSRating, "Title") 
    DADVD.Fill(DSRating, "DVD") 

    'Close the connection to the data store, free up the resources 
    CNRating.Close() 

    'Create a data relation objects between the data tables 
    DSRating.Relations.Add("RatingtoTitle", DSRating.Tables("Rating").Columns("Rating"), DSRating.Tables("Title").Columns("Rating")) 
    DSRating.Relations.Add("TitletoDVD", DSRating.Tables("Title").Columns("Title"), DSRating.Tables("DVD").Columns("Title")) 

    Dim relation As DataRelation 
    Dim table1Column As DataColumn 
    Dim table2Column As DataColumn 

    'retrieve the column 
    table1Column = DSRating.Tables("Rating").Columns("Rating") 
    table2Column = DSRating.Tables("Title").Columns("Rating") 
    'Create a data relation objects between the data tables 
    relation = New DataRelation("relation", table1Column, table2Column) 
    DSRating.Relations.Add(relation) 
    DSRating.Relations.Add("RatingtoTitle", DSRating.Tables("Rating").Columns("Rating"), DSRating.Tables("Title").Columns("Rating")) 
    Try 
     DSRating.Relations.Add("RatingtoTitle", DSRating.Tables("tblVehicle").Columns("Rego_No"), DSRating.Tables("tblRental").Columns("Rego_No")) 

     MsgBox("Data relation completed") 
    Catch ex As Exception 
     MsgBox("Can not open connection ! ") 
    End Try 
End Sub 
End Class 

Answer 1

TitleテーブルにRating列とDVDテーブル内の無Title列はありません。

EDIT：*（すべての列）の代わりに、SELECT文を使用して、列リストを追加し、

Dim DARatings As New OleDb.OleDbDataAdapter("SELECT * FROM Rating", CNRating) 
Dim DATitle As New OleDb.OleDbDataAdapter("SELECT * FROM Title Order By Title", CNRating) 
Dim DADVD As New OleDb.OleDbDataAdapter("SELECT * FROM DVD", CNRating)