invokerequired

问题 I have the following test code. It does nothing useful, but it's there for me to understand VB: Imports System Imports System.IO Imports System.Diagnostics Imports Microsoft.VisualBasic Imports System.Threading Public Class Sandbox Public Shared num As NumericUpDown Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim objWrk As Worker objWrk = New Worker objWrk.Show() End Sub End Class Public Class Worker Public Sub Show() Dim

问题 I have the following test code. It does nothing useful, but it's there for me to understand VB: Imports System Imports System.IO Imports System.Diagnostics Imports Microsoft.VisualBasic Imports System.Threading Public Class Sandbox Public Shared num As NumericUpDown Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim objWrk As Worker objWrk = New Worker objWrk.Show() End Sub End Class Public Class Worker Public Sub Show() Dim

问题 I have the following test code. It does nothing useful, but it's there for me to understand VB: Imports System Imports System.IO Imports System.Diagnostics Imports Microsoft.VisualBasic Imports System.Threading Public Class Sandbox Public Shared num As NumericUpDown Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim objWrk As Worker objWrk = New Worker objWrk.Show() End Sub End Class Public Class Worker Public Sub Show() Dim

问题 I'm building a non-visual component in .Net 2.0. This component uses an asynchronous socket (BeginReceive, EndReceive etc). Asynchronous callbacks are called in the context of a worker thread created by the runtime. The component user shouldn't have to worry about multithreading (This is the main goal, what I want) The component user can create my non-visual component in any thread (the UI thread is just a common thread for simple applications. More serious applications could create the

问题 Project is C#. So I have a bunch of multithreaded code that is designed to be run as a library. It's in a seperate project from the UI. My library has a central object that needs to be created before anything that would fire off events is created. Is it possible for this master object to be passed in some objects so that my events can figure out when they would need to be invoked to get back to the main UI thread? I'd really like to keep the UI from have to do a bunch of invoking since his

问题 how is it possible? I have windows Form control, derived from System.Windows.Forms.Form with WebBrowser control contained in this form. Webbrowser object instance is created in constructor of form (in InitializeComponent() method). Then in background thread I manipulate with content of WebBrowser, and I found that in some cases Form.InvokeRequired == false, while WebBrowser.InvokeRequired == true. How can it be? 回答1: Form.InvokeRequired returns false before the form is shown. I did a simple

问题 What wrong with my code ?? Why it not go to true statement ? 回答1: Your if statement has three conditions - you're only showing two of them in the debugger. I suspect that explains why you're seeing something odd - but I don't think your code is appropriate to start with. For one thing, you're testing the same condition twice, which is pointless (did you mean one of them to be lockScreen rather than loginScreen ?) - but more importantly, if one of those InvokeRequired properties returns false,

问题 This is my code: foreach (var pathCartella in folderList) { try { // some operation if (txtMonitor.InvokeRequired) { txtMonitor.BeginInvoke(new MethodInvoker(delegate { txtMonitor.AppendText(pathCartella + Environment.NewLine); })); } } catch (Exception err) { // some operation return; } } but I notice that, if I catch an Exception, return can act before that all txtMonitor.InvokeRequired has been sent to the UI, and I lost some "message". How can I avoid this? 回答1: If I understand your

问题 I've seen the common setup for cross threading access to a GUI control, such as discussed here: Shortest way to write a thread-safe access method to a windows forms control All the web hits I found describe a similar thing. However, why do we need to check InvokeRequired? Can't we just call Invoke directly? I assume the answer is no, so my real question is 'why'? 回答1: From non-UI threads we can't touch the UI - very bad things can happen, since controls have thread affinity. So from a non-UI

问题 I know that when manipulating UI controls from any non-UI thread, you must marshal your calls to the UI thread to avoid issues. The general consensus is that you should use test InvokeRequired, and if true, use .Invoke to perform the marshaling. This leads to a lot of code that looks like this: private void UpdateSummary(string text) { if (this.InvokeRequired) { this.Invoke(new Action(() => UpdateSummary(text))); } else { summary.Text = text; } } My question is this: can I leave out the