Question

求帮忙看看哪儿错了 啊 要疯了 这是VB.NET里的连接数据库部分的错误 折磨我好久了

错误提示是：
“System.NullReferenceException”类型的未经处理的异常出现在 WindowsApplication1.exe 中。
其他信息: 未将对象引用设置到对象的实例。

报错部分代码是这样的
Public Shared Function Find(ByVal id As String) As Order '按照合同ID号进行查找
aOrder = Nothing
' Define the SQL SQL statement using the phoneno key
Dim sqlQuery As String = "SELECT Customer.CustomerId, CustomerName, phoneNo,vipLevel, " & _
"Order.OrderId,isPaid,totalPayment," & _
"Boat.boatId " & _
" FROM Customer,Order,Boat " & _
" WHERE OrderId='" & id & "'" & _
" AND Boat.boatId = Order.boatId " '& _
' " AND TourRoute.routeId=Boat.routeId"
' Declare dataset
Dim dsOrder As New DataSet
Try ' Execute query & fill dataset
Dim adptOrder As New OleDbDataAdapter(sqlQuery, aConnection)
'adptOrder.Fill(dsOrder, "Order")
' If record in row, found it; extract data
'If dsOrder.Tables("Order").Rows.Count > 0 Then
Dim dr As DataRow
dr = dsOrder.Tables("Order").Rows(0)
'Customer info
customerId = dr("CustomerId")
customerName = dr("CustomerName")
phoneNo = dr("phoneNo")
'historyPayment = dr("historyPayment")
vipLevel = dr("vipLevel")
'groupSize = dr("groupSize")
'Order info
orderId = dr("OrderId")
isPaid = dr("isPaid")
totalPayment = dr("totalPayment")
'groupPoint = dr("groupPoint")
'party info
boatId = dr("boatId")
'departureTime = dr("departureTime")
'currentAmount = dr("currentAmount")
' maxAmount = dr("maxAmount")
rentingCost = dr("rentingCost")
'routeId = dr("routeId")
'days = dr("days")
'route info
' routeId = dr("routeId")
'mainRegion = dr("mainRegion")
'routeDetails = dr("routeDetails")
'isSpecial = dr("isSpecial")
' Create customer & boat instance; assign to customer
aCustomer = New Customer(customerId, customerName, phoneNo, vipLevel)
'aRoute = New Route(routeId, mainRegion, routeDetails, isSpecial)
aBoat = New boat(boatId, rentingCost, boatType, boatState, boatAvailable, deposit)
aOrder = New Order(orderId, isPaid, totalPayment, deposit)
aBoat.AddOrder(aOrder)
aBoat.AddOrder(aOrder)
aOrder.SetCustomer(aCustomer)
aOrder.SetBoat(aBoat)
' Else ' Nothing retrieved, throw error
Throw New NotFoundException("Not Found")
' End If
dsOrder = Nothing
Catch e As OleDb.OleDbException
MessageBox.Show(e.ToString)
End Try
Return aOrder
End Function
937382240 是我的QQ 真心求解 帮我解决问题 有重谢！有酬金。。。真的 这是期末作业啊 今儿晚上就交了 好着急的！跪谢！

Answer 1

“未将对象引用设置到对象的实例”
Fill: SelectCommand.Connection 属性尚未初始化。
--------------------------------------------

估计问题源就出现在这句：
Dim adptOrder As New OleDbDataAdapter(sqlQuery, aConnection)

检查跟踪下 aConnection 是否已实例化，连接数据库字串是否正确！

追问

我不太明白了。。。。能加QQ帮帮我么 我把程序发给你 帮我看看 求救啊。。

追答

你先把连接数据库的那段代码贴出来看看！

追问

那个太长了 我私信给你了 这边字数有限制。。。。

追答

首先你确认已经调用了那个 Initialize() 实例化 aConnection，

然后试试用：
Dim adptOrder As OleDbDataAdapter = New OleDbDataAdapter(sqlQuery, aConnection)

跟踪查看 adptOrder 这个对象的数据，如果连接并查询数据库成功，这个 adptOrder 应该会返回查询的结果集等其它数据，只要adptOrder 里面有数据你下面的代码才不会报错！

追问

Create the SQL statement
Dim sqlInsert As String = "INSERT INTO Order " & _
"VALUES ('" & conId & "', '" & customerId & "', '" & _
boatId & "', " & isPaid & ", " & totalPayment & ", " & deposit & " )"
我的这段插入语句也报错了
这个哪儿有问题呢

Answer 2

设断点跟踪啊，“未将对象引用设置到对象的实例。” 说明 你的sql 没获取到值

追问

从这边开始就不行了
dr = dsCustomer.Tables("Customer").Rows(0)
customerId = dr("customerId")
customerName = dr("customerName")
phoneNo = dr("phoneNo")
vipLevel = dr("vipLevel")
把那些都设置断点之后。。。
在下边的 adptCustomer.Fill(dsCustomer, "Customer")
出现了个这个
Fill: SelectCommand.Connection 属性尚未初始化。

追答

dsCustomer.Tables[0].Rows.Count>0
dr = dsCustomer.Tables("Customer").Rows(0)
customerId = dr("customerId")
customerName = dr("customerName")
phoneNo = dr("phoneNo")
vipLevel = dr("vipLevel")

追问

大神 dsCustomer.Tables[0].Rows.Count>0
我那个语句上边有。。。恩

追答

写 .net 的 写习惯了