.Net中的"InvokeRequired"和"Invoke"是什么意思? [英] What does 'InvokeRequired' and 'Invoke' mean in .Net?

问题描述

我已经在我正在处理的一些程序中使用线程进行了大量工作，而我一直很好奇到底在做什么.

I have been working a lot with threading in a few programs I am working on, and I have always been curious as to what exactly something is doing.

以下面的代码为例，该代码是从线程运行以更新UI的:

Take for instance the following code, which is ran from a thread to update the UI:

Public Sub UpdateGrid() 
    If Me.InvokeRequired Then 
        Me.Invoke(New MethodInvoker(AddressOf UpdateGrid)) 
    Else 
        DataGridView1.DataSource = dtResults 
        DataGridView1.Refresh() 
        btnRun.Text = "Run Query" 
        btnRun.ForeColor = Color.Black 
    End If 
End Sub

Me.InvokeRequired到底要检查什么，Me.Invoke到底要做什么?我知道，它以某种方式使我可以访问UI上的项目，但是它是如何实现的呢?

What exactly does the Me.InvokeRequired check for, and what exactly is the Me.Invoke doing? I understand that somehow it gives me access to items on the UI, but how does it accomplish this?

另一方面，假设UpdateGrid()是一个返回值并具有必需参数的函数.调用Me.Invoke方法后，如何传递参数以及如何获得返回值?我尝试了没有参数的尝试，但是没有返回"nothing"，并且我无法弄清楚在调用时如何附加参数.

On a side note, let's say UpdateGrid() was a function that returned a value and had a required parameter. How would I pass the parameter and how would I get the return value after I call the Me.Invoke method? I tried this without the parameter but 'nothing' was getting returned, and I couldn't figure out how to attach the parameter when invoking.

推荐答案

Me.InvokeRequired正在检查它是否在UI线程上，如果不等于True，则Me.Invoke要求委托来处理之间的通信diff线程.

Me.InvokeRequired is checking to see if it's on the UI thread if not it equals True, Me.Invoke is asking for a delegate to handle communication between the diff threads.

至于你的旁注.我通常使用一个事件来传递数据-该事件仍在diff线程上，但是像上面一样，您可以委派工作.

As for your side note. I typically use an event to pass data - this event is still on the diff thread, but like above you can delegate the work.

Public Sub UpdateGrid() 
    'why ask if I know it on a diff thread
    Me.Invoke(Sub() 'lambda sub
               DataGridView1.DataSource = dtResults 
               DataGridView1.Refresh() 
               btnRun.Text = "Run Query" 
               btnRun.ForeColor = Color.Black 
              End Sub)
End Sub

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