每次我在數據庫上搜索時,它總是說「對象引用未設置爲對象的實例」。 請大家幫幫我。謝謝。未將對象引用設置爲對象的實例VB.Net OleDbCommand
這裏是我的代碼搜索:
Private Sub BtnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSearch.Click
If TBSearch.Text = "" Then
MsgBox("Please enter keyword to search...", MsgBoxStyle.Information, "Keyword to search...")`
TBSearch.Focus()
Exit Sub
End If
Call OpenConnection()
With OleDa
Call Initialized()
.SelectCommand = New OleDb.OleDbCommand() <-------- Error appears here.
.SelectCommand.CommandText = "SELECT * FROM [HighSchool] WHERE [LastName] Like '%%" & TBSearch.Text & "%%' or [FirstName] Like '%%" & TBSearch.Text & "%%' or [MI] Like '%%" & TBSearch.Text & "%%'" & _
"Or [Gender] Like '%%" & TBSearch.Text & "%%' or [Address] Like '%%" & TBSearch.Text & "%%' or [Birthday] Like '%%" & TBSearch.Text & "%%' or [RNumber] Like '%%" & TBSearch.Text & "%%'" & _
"Or [ENumber] Like '%%" & TBSearch.Text & "%%' ORDER By LastName ASC"
.SelectCommand.Connection = OleCn
Call PopulateListView()
If Me.LV.Items.Count >= 1 Then
MsgBox(Me.LV.Items.Count & " Record(s) found for " & "(" & Me.TBSearch.Text & ")", MsgBoxStyle.OkOnly, "Record(s) found...")
Else
MsgBox("No record(s) found for " & "(" & Me.TBSearch.Text & ")" & " , please try again... ", MsgBoxStyle.Critical, "No record found...")
TBSearch.Focus()
TBSearch.SelectAll()
End If
End With
Call CloseConnection()
End Sub
這裏是我的填充ListView控件代碼:
Public Sub PopulateListView() Me.LV.Items.Clear() Dim OleDr As OleDb.OleDbDataReader OleDr = OleDa.SelectCommand.ExecuteReader()
Do While OleDr.Read()
Dim Item As New ListViewItem
Item.Text = IIf(OleDr.IsDBNull(0), "", OleDr.Item(0))
For shtCntr = 1 To OleDr.FieldCount() - 1
If Not OleDr.IsDBNull(shtCntr) Then
Item.SubItems.Add(OleDr.Item("FirstName"))
Item.SubItems.Add(OleDr.Item("LastName"))
Item.SubItems.Add(OleDr.Item("MI"))
Item.SubItems.Add(OleDr.Item("Gender"))
Item.SubItems.Add(OleDr.Item("Address"))
Item.SubItems.Add(OleDr.Item("Birthday"))
Item.SubItems.Add(OleDr.Item("RNumber"))
Item.SubItems.Add(OleDr.Item("ENumber"))
Else
Item.SubItems.Add("")
End If
Next shtCntr
Me.LV.Items.Add(Item)
Loop
End Sub
哪一行是拋出錯誤? – 2014-12-08 08:01:36
.SelectCommand =新OleDb.OleDbCommand()<---在這裏錯誤sir – user2926827 2014-12-08 08:04:27
可能重複[什麼是NullReferenceException,我該如何解決它?](http://stackoverflow.com/questions/4660142/what- is-a-nullreferenceexception-and-how-do-i-fix-it) – Plutonix 2014-12-08 12:43:35