UC知道vb.net 求救啊，“未将对象引用设置到对象实例”
来源：百度知道 编辑：UC知道 时间：2024/05/04 10:43:11
Dim pbalance As Single
Dim tSum As Double = 0
Dim tConn As OleDbConnection = New OleDbConnection
Dim tComm As New OleDbCommand
Dim tReader As OleDbDataReader
tConn = New OleDbConnection(("PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA SOURCE=" & Application.StartupPath + "\data.mdb"))
tComm.Connection = tConn
tComm.CommandText = "select p_balance from payments"
tConn.Open()
'tReader = tComm.ExecuteReader
While tReader.Read = True /程序在这里断了
pbalance = tReader.GetFloat(0)
tSum = tSum + pbalance
End While
tConn.Close()
Label19.Text = tSum
请大家帮帮忙~
While tReader.Read = True /程序在这里断了
这里改了下 While tReader.Read 还是同样的错
Dim tSum As Double = 0
Dim tConn As OleDbConnection = New OleDbConnection
Dim tComm As New OleDbCommand
Dim tReader As OleDbDataReader
tConn = New OleDbConnection(("PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA SOURCE=" & Application.StartupPath + "\data.mdb"))
tComm.Connection = tConn
tComm.CommandText = "select p_balance from payments"
tConn.Open()
'tReader = tComm.ExecuteReader
While tReader.Read = True /程序在这里断了
pbalance = tReader.GetFloat(0)
tSum = tSum + pbalance
End While
tConn.Close()
Label19.Text = tSum
请大家帮帮忙~
While tReader.Read = True /程序在这里断了
这里改了下 While tReader.Read 还是同样的错
这位朋友
你改成：while tReader.Read()
就可以了
你试试，应该是对的，除非你程序本身有问题！
祝你早日解决问题！
朋友还在吗？怎么不回话！
问题解决了没有？
'tReader = tComm.ExecuteReader
这行注释掉了，没有执行。
While tReader.Read = True /程序在这里断了
这行中的“tReader”就是nothing了。
把上面的注释去掉就没事了。
imports system.data
imports system.data.oledb
.
.
Dim pbalance As Single
Dim tSum As Double = 0
Dim tConn As OleDbConnection = New OleDbConnection
Dim tComm As OleDbCommand
Dim tReader As OleDbDataReader
tConn = New OleDbConnection(("PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA SOURCE=" & Application.StartupPath + "\data.mdb"))
tComm.Connection = tConn
tComm.CommandText = "select p_balance from payments"
tConn.Open()
tComm =new oledbcommand("select p_balance from payments",tConn)
tReader = tComm.ExecuteReader()
While tReader.Read = True /程序在这里断了
pbalanc