Visual Studio 2012 - 自动更改文本框 [英] Visual studio 2012 - change text box automatically

问题描述

我使用Visual Studio 2012，



i想根据固定的组合框值自动更改文本框值，



意味着我有4个固定值的组合框和&我想根据这些可变值更改另一个文本框值。



所以任何人都知道应用的简单方法会很棒



谢谢..，





以前的解决方案不起作用，我需要做出如下条件：

Iam using Visual studio 2012,

i would like to change text box values automatically based on fixed combo box values,

meaning i have combobox with 4 fixed values & i want to change another text box values based on these changeable values.

so anyone know simple method to apply that will be great

thanks..,


the previous solution didn't work, i need to make condition like:

If fy.Text = 2400 Then
    µmax.Text = 8.56 / 100000 * fcu.Text

ElseIf fy.Text = 2800 Then
    µmax.Text = 7 / 100000 * fcu.Text

ElseIf fy.Text = 3600 Then
    µmax.Text = 5 / 100000 * fcu.Text

ElseIf fy.Text = 4000 Then
    µmax.Text = 4.31 / 100000 * fcu.Text

End If

（fy是组合框名称）（μmax是文本框名称）



'我也试过这个，但是没用了

(fy is the combobox name) ( µmax is the textbox name)

' i tried this also, but it didn't work

Private Sub fy_SelectedIndexChanged(sender As Object, e As EventArgs) Handles fy.SelectedIndexChanged


        If fy.SelectedIndex = 2400 Then
            µmax.Text = 8.56 / 100000 * fcu.Text

        
        ElseIf fy.SelectedIndex = 3600 Then
            µmax.Text = 7 / 100000 * fcu.Text

        End If

    End Sub

推荐答案

您的尝试有几个问题。最重要的是，您正在尝试混合数字数据和字符串数据。有时你会得到一个为你的隐式转换，但你永远不要依赖它。



在你的第二次尝试中你会感到困惑 SelectedIndex （列表中所选项目的排名）和 SelectedItem （选择的实际项目）。 - 我怀疑你在comboBox中有3600个项目。



而不是多个如果语句考虑使用某种形式的查找（浏览 sergey的解决方案 [ ^ ]我知道他已经写了几个很好的解决方案主题）



我已经测试了这段代码并且它可以工作

You have several issues with your attempts. Most importantly you are trying to mix numeric data and string data. Sometimes you will get an implicit conversion done "for you" but you should never rely on this.

In your second attempt you are confusing SelectedIndex (the rank of the selected item within the list) and SelectedItem (the actual item selected). - I somehow doubt that you have 3600 items in the comboBox fy.

Instead of having multiple if statements consider using some form of lookup (have a look through sergey's solutions[^] as I know he's written several good solutions on this subject)

I've tested this code and it works

Dim factors As Double() = {8.56, 7, 5, 4.31} 'etc
Const multiplier As Double = 10000.0

Dim fcuAsDouble As Double
If Not Double.TryParse(fcu.Text, fcuAsDouble) Then
    'raise an error not a valid number
End If

Dim result As Double = (factors(fy.SelectedIndex) / multiplier) * fcuAsDouble

umax.Text = result.ToString()

因素是我对y的查找我们在多个if语句中使用的值。我使用了一个简单的数组，但还有其他（和更好的）选项。



我还定义了乘数作为常数，因为我不喜欢魔术数字



接下来我查看 fcu 文本框并将其文本转换为双，以便我可以在计算中使用它。注意使用 Double.TryParse（） - 如果格式正确，它会将文本转换为Double值，否则返回False。如果包含fcu，Double.Parse会出错（例如）三



在下一行中我使用 fy.Selected 索引 从我的数组中查找相应的因子，并计算结果。



最后当我将结果分配到umax文本框我使用将其转换为文本ToString（）



以上所有我放入根据我之前的评论 fy_SelectedIndexChanged 事件

factors is my lookup for your values that you are using in your multiple if statements. I've used an array for simplicity but there are other (and better) options.

I've also defined multiplier as a constant because I don't like "magic numbers"

Next I look to the fcu textbox and convert it's text into a double so I can use it in the calculation. Note the use of Double.TryParse() - it will convert text into a Double value if in the right format otherwise it will return False. Double.Parse will error if fcu contained (for example) "three"

In the next line I use fy.SelectedIndex to look up the appropriate factor from my array, and work out the result.

Finally when I assign the result into the umax text box I convert it to text using ToString()

All of the above I put into the fy_SelectedIndexChanged event as per my earlier comments

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