急死了！！！！大家帮帮忙！！！我自定义了一个过程，但是调用得时候，出现下面得错误，大家帮我看看哟！！！

[yqyzzy]

错误！！！


“/wenzhang”应用程序中的服务器错误。
--------------------------------------------------------------------------------

未将对象引用设置到对象的实例。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

源错误:


行 62： Dim i As Integer
行 63： i = 0
行 64： cmdoledb.Connection.Open()
行 65： cmdoledb.CommandText = "select top 1 fatherid from [class] where classname='" & str1 & "'"
行 66： i = Convert.ToInt32(cmdoledb.ExecuteScalar())


源文件: D:\zyweb\wenzhang\addclass.aspx.vb 行: 64



源代码：

Sub addclass(ByVal sender As Object, ByVal e As EventArgs)
Dim str, str1, sql As String

Dim cnn As New conn
cnn.con3.Open()
If DropDownList1.SelectedValue = "" Then
str = TextBox1.Text
sql = "insert into class (classname,fatherid) values(' " & str & "','" & 0 & "')"
Dim adapter As New OleDbCommand(sql, cnn.con3)
adapter.ExecuteNonQuery()
Else
str = TextBox2.Text
str1 = DropDownList1.SelectedValue
Dim cmdoledb As New OleDbCommand
Dim i As Integer
i = 0
cmdoledb.Connection.Open()
cmdoledb.CommandText = "select top 1 fatherid from [class] where classname='" & str1 & "'"
i = Convert.ToInt32(cmdoledb.ExecuteScalar())
sql = "insert into [class] (classname,fatherid) values('" & str & "','" & i & "')"
Dim cmdoledb1 As New OleDbCommand(sql, cnn.con3)
cmdoledb1.ExecuteNonQuery()
End If
End Sub

[guanvee]

你好像没有指定cmdoledb的connection对象吧

[yqyzzy]

对，我也是这样想得，可以把代码写出来看看嘛！！！

[derny]

Dim cmdoledb As New OleDbCommand //cmdoledb 还没赋值怎么就用咯？
Dim i As Integer
i = 0
cmdoledb.Connection.Open()

[bitsbird]

str1 是什么?

[yqyzzy]

str1 = DropDownList1.SelectedValue

[cnhgj]

cmdoledb = new OleDbCommand()??

[wd_318]

2004-08-26 18:50:53 浪花
IT人,你的查询没有结果嘛,上次已经和你说过,要检查返回结果是否为NULL


2004-08-26 18:51:55 浪花
如果结果是NULL,
Convert.ToInt32()可能会出错的

[wd_318]

Dim obj as Object =cmdoledb.ExecuteScalar()
if(null = obj)
'没有结果
else
i = Convert.ToInt32(obj)

不用VB。NET，不知道if else 是不是有问题，自己改一下

[derny]

行 64： cmdoledb.Connection.Open()
肯定就是cmdoledb为null！
你跟踪调试看看cmdoledb的值是多少
VB我不是很熟。。。

[wd_318]

Dim cmdoledb As New OleDbCommand
Dim i As Integer
i = 0
cmdoledb.Connection.Open()
cmdoledb.CommandText = "select top 1 fatherid from [class] where classname='" & str1 & "'"
i = Convert.ToInt32(cmdoledb.ExecuteScalar())

'同意 guanvee(答对就给分)
你没有指定cmdoledb的connection对象

[yqyzzy]

自己顶一下！

[saucer]

where is your connection object???

dim cmdconn as New OleDbConnection("YourConnectionStringHere")

Dim cmdoledb As New OleDbCommand

cmdoledb.COnnection = cmdconn


or

Dim cmdoledb As New OleDbCommand
cmdoledb.Connection = cnn.con3

[gxboy]

思老大你是在抢生意啊。