Vb.net数据库问题

我正在为我的女友编写卡路里计数器工具...

但是我遇到了一个我真的不知道的问题...

我在脚本中有个地方想要从数据库中获取一些信息...

在脚本中取笑的特定位置是将从称为“ items”的表中的“ antal”行中取出数据的位置。

在脚本中的一个地方，我从项目中称“ navn”，它的工作原理非常完美...

在另一个地方，它给我一个错误，即行中没有任何数据！

我的代码到目前为止看起来像这样：

Imports System.Data.OleDb

Private Sub ins_kat_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ins_kat.SelectedIndexChanged
Dim Con = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\Privat\MCC\mccdb.mdb")
Con.Open()
Dim command As OleDbCommand = New OleDbCommand("SELECT * FROM items WHERE kat = '" & ins_kat.Text & "' ORDER BY id DESC", Con)
Dim read As OleDbDataReader = command.ExecuteReader()
ins_mad.Items.Clear()
While read.Read()
ins_mad.Items.Add(read.Item("navn")) '<---- This place works!!!
End While
Con.Close()
End Sub

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click

Dim ialt_c_counter As String
Dim ialt_c_counter_conv As Decimal
Dim ialt_c_counter_conv2 As Decimal
Dim ialt_counter As String
Dim ialt_final As Decimal


Dim Con = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\Privat\MCC\mccdb.mdb")
Con.Open()
Dim command1 As OleDbCommand = New OleDbCommand("SELECT * FROM food WHERE dag = '" & stat_dag.Text & "' AND maaned = '" & stat_maaned1.Text & "' AND aar = '" & stat_aar1.Text & "'", Con)

Dim read1 As OleDbDataReader = command1.ExecuteReader()

While read1.Read()
ialt_c_counter = read1.Item("antal")
ialt_c_counter_conv = System.Convert.ToDecimal(ialt_c_counter)

Dim commandX As OleDbCommand = New OleDbCommand("SELECT * FROM items", Con)
Dim reader As OleDbDataReader = commandX.ExecuteReader()

ialt_counter = reader.Item("antal") '<--- THIS ONE is giving me the error!!
ialt_c_counter_conv2 = System.Convert.ToDecimal(ialt_counter)

ialt_final = (ialt_c_counter_conv / 100 * ialt_c_counter_conv2) + ialt_final

End While

Con.Close()
MsgBox(ialt_final)
End Sub
End Class

现在，我想要一个MsgBox告诉我算法的结果，但是我什至没有得到导致错误消息的原因……