主题：[求助]未将对象引用到实例

以下内容为程序代码:

1 Dim cmb As WinForm.ComboBox = e.Form.Controls("UserName")
2 cmb.ComboList = _UserTable.SQLGetComboListString("Name")

以下内容为程序代码:

1 Dim UserName As String = e.Form.Controls("UserName").Value
2 Dim dr As DataRow
3 If UserName = "" Then
4 Messagebox.show("请选择用户!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
5 Return
6 End If
7 dr = _UserTable.SQLFind("[Name] = '" & UserName & "'")
8 If dr Is Nothing Then
9 Messagebox.show("此用户不存在!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
10 Return
11 End If
12 If e.Form.Controls("PassWord").Value = dr("Password") Then
13 _UserName = UserName
14 _UserGroup = dr("Group")
15 e.Form.Close
16 Else
17 Messagebox.show("密码错误!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
18 End If