vb.net BringToFront 并没有将形式带到前面
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BringToFront isn't bringing form to the front
提问by Sean Long
I'm trying to set up a button that does the following:
我正在尝试设置一个执行以下操作的按钮：
- Checks to see if a form is open (and has lost focus). If so, it brings that form to the front.
- If not, it opens a new instance of the form.
- 检查表单是否已打开（并且已失去焦点）。如果是这样，它会将这种形式带到前面。
- 如果没有，它会打开一个新的表单实例。
However, I've tried a few different methods and it will always either create a new form (if I use frm_About.visible as the check) or simply not do anything (with the following code).
但是，我尝试了几种不同的方法，它总是会创建一个新表单（如果我使用 frm_About.visible 作为检查）或者根本不做任何事情（使用以下代码）。
Private Sub counter_aboutClick(sender As Object, e As EventArgs) Handles counter_About.Click
If Application.OpenForms().OfType(Of frm_About).Any Then
frm_About.BringToFront()
Else
Dim oAbout As frm_About
oAbout = New frm_About()
oAbout.Show()
oAbout = Nothing
End If
End Sub
I've heard that there's a bug with BringToFront in certain scenarios, am I hitting that bug?
我听说在某些情况下BringToFront 存在错误，我是否遇到了该错误？
回答by J...
VB.Net does a terrible thing and creates a default instance of a form (which can be referred to by its class name). This creates endless confusion and headaches - I suggest you read up on default instances (google can find a lot to read about, surely)
VB.Net 做了一件很糟糕的事情并创建了一个表单的默认实例（可以通过它的类名来引用）。这会造成无休止的混乱和头痛 - 我建议您阅读默认实例（谷歌可以找到很多可以阅读的内容，当然）
In this case, you have a class called frm_Aboutas well as a default instance of that form which is also called frm_About. If you've created a new form of type frm_Aboutthen the following code
在这种情况下，您有一个名为 的类frm_About以及该表单的默认实例，该实例也称为frm_About。如果你已经创建了一个新的表单类型，frm_About那么下面的代码
If Application.OpenForms().OfType(Of frm_About).Any Then
frm_About.BringToFront()
will search your open forms to look for a form of type frm_Aboutand, if it finds one, will attempt to bring the default instance of frm_Aboutto the front - note that the open form can be (an in your case is most likely) not the default instance but any instance created with New frm_About().
将搜索您打开的表单以查找一种类型的表单frm_About，如果找到，将尝试将默认实例frm_About放在前面 - 请注意，打开的表单可以（在您的情况下很可能）不是默认的实例，但任何使用New frm_About().
To find the actual instance of the form you would have to do something like :
要找到表单的实际实例，您必须执行以下操作：
For Each openForm In Application.OpenForms()
If TypeOf (openForm) Is frm_About Then _
CType(openForm, frm_About).BringToFront()
Next
