VB.net使用扩展方法避免跨线程异常 [英] VB.net avoiding cross thread exception with extension method

问题描述

你好 我正在尝试实现一种无需使用委托即可更新表单控件的解决方案.

Hello I am trying to implement a solution for updating form controls without using a delegate.

我正在尝试使用此页面上的第一种解决方案:

I am attempting to use the 1st solution on this page:

http://www.dreamincode.net/forums/blog/143/entry-2337-handling-the-dreaded-cross-thread-exception/

Imports System.ComponentModel
Imports System.Runtime.CompilerServices

Public Module MyInvoke
    <Extension()> _
    Public Sub CustomInvoke(Of T As ISynchronizeInvoke)(ByVal control As T, ByVal toPerform As Action(Of T))
        If control.InvokeRequired Then
            control.Invoke(toPerform, New Object() {control})
            toPerform(control)
        End If
    End Sub
End Module

该网站以使用方式为例:

The site gives this as example of how to use:

Label1.CustomInvoke(l => l.Text = "Hello World!")

但是我得到的'l'没有被声明为错误. 如您所见，这对VB或任何OOP来说都是很新的东西.

But i get 'l' is not declared error. As you can see im very new to VB or any OOP.

我可以在该页面上使用工作台上的第二个解决方案(使用委托)，但是我在该线程中有很多工作要做，似乎我需要为每件事编写一个新的委托子，这似乎很浪费

I can get the second solution on that page to work (using delegates) but i have quite a few things to do in this thread and it seems like i would need to write a new delegate sub for each thing, which seems wasteful.

我需要做的是从组合框中选择第一个项目，用选定的项目更新textbox.text，然后将选定的项目传递给函数. 然后等待x秒，然后重新开始，选择第二项.

What i need to do is select the 1st item from a combobox, update a textbox.text with the selected item, and pass the selected item to a function. Then wait for x seconds and start again, selecting the second item.

我可以让它在单线程应用程序中工作，但是我需要接口保持响应.

I can get it to work in a single threaded application, but i need the interface to remain responsive.

任何帮助都将不胜感激.

Any help greatly appreciated.

好的，因此更改语法适用于该示例. 但是，如果我将其更改为

OK so changing the syntax worked for the example. However if i change it from

Label1.CustomInvoke(Sub(l) l.text = "hello world!")

(效果很好):

Dim indexnumber As Integer = 0
ComboBox1.CustomInvoke(Sub(l) l.SelectedIndex = indexnumber)

我收到跨线程错误，好像我什至没有使用此方法一样:

I get a cross threading error as though i didnt even use this method:

Cross-thread operation not valid: Control 'ComboBox1' accessed from a thread other than the thread it was created on.

所以现在我回到我的起点了吗? 非常感谢任何帮助.

So now im back to where i started? Any further help very much appreciated.

推荐答案

第二期；我认为您需要添加其他内容:

Per your second issue; I think you need to add an Else:

Public Sub CustomInvoke(Of T As ISynchronizeInvoke)(ByVal control As T, ByVal toPerform As Action(Of T))
    If control.InvokeRequired Then
        control.Invoke(toPerform, New Object() {control})
    Else
'   ^^^^
        toPerform(control)
    End If
End Sub 

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