如何使用退格键清除列表框，以便输入新值 [英] How to use backspace key to clear listbox so you can enter in a new value

问题描述

我正在制作一个乘法图表，当你点击显示时，它会在列表框中显示数字1-9的文本框中的数字，但我遇到的问题是，如果我点击退格并输入一个新的号码，它不会清除旧的列表，并将
的新列表放在框中。我已经环顾四周，并试图找出如何编码它来刷新列表再次点击显示按钮，但我不知道如何，所以任何帮助将不胜感激。 

    Private Sub DisplayButton_Click（发件人为对象，e为EventArgs）处理DisplayButton.Click

  &NBSP; &NBSP; &NBSP; Do While（num< = 9）

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; ListBox.Items.Add（Val（NumbertxtBox.Text）&" *"& num&" ="& num * Val（NumbertxtBox.Text））

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; num + = 1

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; ListBox.Refresh（）

  &NBSP; &NBSP; &NBSP;循环



  &NBSP; &NBSP; &NBSP;如果是Integer.TryParse（NumbertxtBox.Text，num）则为


  &NBSP; &NBSP; &NBSP;否则

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; MessageBox.Show（"请输入数字"）

  &NBSP; &NBSP; &NBSP;结束如果






  &NBSP;结束点¥b $ b结束等级

解决方案

它不会清除旧列表并将新列表放在框中。  

  &NBSP; Private Sub DisplayButton_Click（发件人为对象，e为EventArgs）处理DisplayButton.Click

  &NBSP; &NBSP; &NBSP; Do While（num< = 9）

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; ListBox.Items.Add（Val（NumbertxtBox.Text）&" *"& num&" ="& num * Val（NumbertxtBox.Text））

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; num + = 1

  &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; ListBox.Refresh（）

  &NBSP; &NBSP; &NBSP;循环



$

首先，请注意，此论坛适用于C＃问题，您的代码是Visual Basic。

您应该在Visual Basic论坛中发布。



关于清除ListBox，您是否尝试在添加项目之前将其清除？

例如：

 Private Sub DisplayButton_Click（sender As Object，e As EventArgs）处理DisplayButton.Click 
 ListBox.Items.Clear（）
 Do While（num< = 9）
 ListBox.Items.Add（Val（NumbertxtBox.Text）&" *"& num&" ="& num * Val（NumbertxtBox.Text））
 num + = 1 
 ListBox.Refresh（）
 Loop 
 

- Wayne

I am making a multiplication chart that when you hit display it will show in a list box the number from the text box mutiplied by numbers 1-9, but i am having the problem that if i hit backspace and enter a new number it will not clear the old list and put the new list in the box. I have looked around and tried to figure out how to code it to refresh the list when hitting the display button again but i dont know how to so any help would be much appreciated. 

    Private Sub DisplayButton_Click(sender As Object, e As EventArgs) Handles DisplayButton.Click
        Do While (num <= 9)
            ListBox.Items.Add(Val(NumbertxtBox.Text) & "*" & num & "=" & num * Val(NumbertxtBox.Text))
            num += 1
            ListBox.Refresh()
        Loop

        If Integer.TryParse(NumbertxtBox.Text, num) Then

        Else
            MessageBox.Show("Please Enter a Number")
        End If



    End Sub
End Class

解决方案

it will not clear the old list and put the new list in the box.  

    Private Sub DisplayButton_Click(sender As Object, e As EventArgs) Handles DisplayButton.Click
        Do While (num <= 9)
            ListBox.Items.Add(Val(NumbertxtBox.Text) & "*" & num & "=" & num * Val(NumbertxtBox.Text))
            num += 1
            ListBox.Refresh()
        Loop

First, note that this forum is for C# issues and your code is Visual Basic.
You should have posted in the Visual Basic forum.

As to clearing the ListBox, have you tried clearing it before adding items?
For example:

 Private Sub DisplayButton_Click(sender As Object, e As EventArgs) Handles DisplayButton.Click
        ListBox.Items.Clear()
        Do While (num <= 9)
            ListBox.Items.Add(Val(NumbertxtBox.Text) & "*" & num & "=" & num * Val(NumbertxtBox.Text))
            num += 1
            ListBox.Refresh()
        Loop

- Wayne

这篇关于如何使用退格键清除列表框，以便输入新值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！