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我从网上得到了这段代码,但是我不能让这段代码在系统上工作,我正在编程,所以我使用了相同的代码到另一个系统,它工作,当我尝试使用它我的系统,它失败了,所以我开始了一个新的程序,它仍然失败...我的程序有什么问题?这里是代码的示例:Vb 10空引用异常
Public Class Form2
Dim con As New OleDb.OleDbConnection
Dim dbProvider As String
Dim dbSource As String
Dim ds As New DataSet
Dim da As OleDb.OleDbDataAdapter
Dim sql As String
Dim inc As Integer
Dim max As Integer
Private Sub AllRecordsToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
dbProvider = "PROVIDER = Microsoft.Jet.OLEDB.4.0;"
dbSource = "Data Source = C:\Users\Josh\Documents\enrollment.mdb"
con.ConnectionString = dbProvider & dbSource
con.Open()
sql = "SELECT * FROM Personal"
da = New OleDb.OleDbDataAdapter(sql, con)
da.Fill(ds, "enrollment")
max = ds.Tables("enrollment").Rows.Count
inc = -1
con.Close()
Private Sub Sve_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Sve.Click
If inc <> -1 Then
Dim cb As New OleDb.OleDbCommandBuilder(da)
Dim dsnewrow As DataRow
dsnewrow = ds.Tables("enrollment").NewRow()
dsnewrow.Item("LastName") = TextLast.Text
ds.Tables("enrollment").Rows.Add(dsnewrow)
da.Update(ds, "enrollment")
MsgBox("Saved!")
End If
End Sub
每当我运行程序,它编译,但是当我点击提交按钮,显示此消息“NullReference例外是未处理的对象引用不设置为一个对象的一个实例“和它指向.NewRow