vb.net 对于每个文本框循环
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For each textbox loop
提问by Lift
I'm trying to make a foreach loop that checks every TextBox in a panel and changes BackColor if its Text is nothing. I've tried the following:
我正在尝试创建一个 foreach 循环来检查面板中的每个 TextBox，如果它的 Text 什么都没有，则更改 BackColor。我尝试了以下方法：
Dim c As TextBox
For Each c In Panel1.Controls
if c.Text = "" Then
c.BackColor = Color.LightYellow
End If
Next
but I'm getting the error:
但我收到错误：
Unable to cast object of type System.Windows.Forms.Label to type System.windows.forms.textbox
无法将 System.Windows.Forms.Label 类型的对象转换为 System.windows.forms.textbox
回答by Neolisk
Assuming there are no nested controls:
假设没有嵌套控件：
For Each c As TextBox In Panel1.Controls.OfType(Of TextBox)()
If c.Text = String.Empty Then c.BackColor = Color.LightYellow
Next
回答by Colin Pear
You might try something like this instead:
你可以试试这样的：
Dim ctrl As Control
For Each ctrl In Panel1.Controls
If (ctrl.GetType() Is GetType(TextBox)) Then
Dim txt As TextBox = CType(ctrl, TextBox)
txt.BackColor = Color.LightYellow
End If
回答by Derek Tomes
Try this. It'll put the color back when you enter data as well
尝试这个。当您输入数据时，它也会恢复颜色
For Each c As Control In Panel1.Controls
If TypeOf c Is TextBox Then
If c.Text = "" Then
c.BackColor = Color.LightYellow
Else
c.BackColor = System.Drawing.SystemColors.Window
End If
End If
Next
There is also a different way to do this which involves creating an inherited TextBox control and using that on your form:
还有一种不同的方法可以做到这一点，包括创建一个继承的 TextBox 控件并在您的表单上使用它：
Public Class TextBoxCompulsory
Inherits TextBox
Overrides Property BackColor() As Color
Get
If MyBase.Text = "" Then
Return Color.LightYellow
Else
Return DirectCast(System.Drawing.SystemColors.Window, Color)
End If
End Get
Set(ByVal value As Color)
End Set
End Property
End Class
