如何检查是否未选中组合框和选中的列表框 [英] How to check if Combo box and checked listbox are not selected

问题描述

Hello Experts，



我的Windows窗体中有一个Textbox，Checked列表框和组合框。现在我必须让我的程序处于这样一个控制之中，应该输入这三个中的任何一个。例如，如果我输入文本框，我必须检查是否未选中组合框和选中的列表框。只有这样我才能运行我的功能。

这是我试过的东西

Hello Experts,

I have a Textbox, Checked listbox and Combo box in my windows form. Now I have to make my program in such a sway that, any one of these three should be entered. For example, If I enter Textbox, I have to check if Combo box and Checked Listbox are not selected. Only then I have to run my function.
Here is what I tried

If txtAccount.Text.ToString().Length() > 0 Then
      If cmbProgram.SelectedItem.ToString().Length = 0 Or   chkClasslist.SelectedItem.ToString().Length = 0 Then
        Panel2.Visible = True

End If

我得到的Object引用未设置为实例...



有人可以帮助我实现我的req.?

And I get Object reference not set to instance...

Could someone help me to achieve my req.?

推荐答案

使用字符串。 IsNullOrEmpty（）而不是ToString（）。长度= 0





如果不是String.IsNullOrEmpty（txtAccount.Text）那么

如果String.IsNullOrEmpty（cmbProgram.Text）或String.IsNullOrEmpty（Convert.ToString（cmbProgram） .SelectedItem））或String.IsNullOrEmpty（chkClasslist.Text）或String.IsNullOrEmpty（Convert.ToString（chkClasslist.SelectedItem））然后

Panel2.Visible = True

结束如果

结束如果



谢谢

Hi,



Use "String.IsNullOrEmpty()" instead of ToString().Length = 0


If Not String.IsNullOrEmpty(txtAccount.Text) Then
If String.IsNullOrEmpty(cmbProgram.Text) Or String.IsNullOrEmpty(Convert.ToString(cmbProgram.SelectedItem)) Or String.IsNullOrEmpty(chkClasslist.Text) Or String.IsNullOrEmpty(Convert.ToString(chkClasslist.SelectedItem)) Then
Panel2.Visible = True
End If
End If

Thanks

Try this!

If（txtAccount.Text<> String.Empty AndAlso cmbProgram.SelectedItem is Nothing AndAlso chkClasslist.SelectedItem is Nothing）orelse



（txtAccount.Text = String.Empty AndAlso cmbProgram.SelectedItem isNot Nothing AndAlso chkClasslist。 SelectedItem没什么）



orelse



（txtAccount.Text = String.Empty AndAlso cmbProgram.SelectedItem is什么AndOso chkClasslist.SelectedItem isNot Nothing）



然后

Panel2.Visible = True



结束如果

If (txtAccount.Text <> String.Empty AndAlso cmbProgram.SelectedItem is Nothing AndAlso chkClasslist.SelectedItem is Nothing) orelse

(txtAccount.Text = String.Empty AndAlso cmbProgram.SelectedItem isNot Nothing AndAlso chkClasslist.SelectedItem is Nothing)

orelse

(txtAccount.Text = String.Empty AndAlso cmbProgram.SelectedItem is Nothing AndAlso chkClasslist.SelectedItem isNot Nothing)

Then
Panel2.Visible = True

End If

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