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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘WinForms’ Category

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Dear fellow programmer. If you aren’t experienced doing multi-threading, please don’t!

Posted by jpluimers on 2012/07/05

Recently I was asked to investigate a performance problem with a certain .NET application.

The first error I got when getting the app to build in Visual Studio 2010, and then run it was like this:

System.ComponentModel.InvalidAsynchronousStateException was caught
  Message=An error occurred invoking the method.  The destination thread no longer exists.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.Control.WaitForWaitHandle(WaitHandle waitHandle)
       at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
       at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
       at UI.Splash.SetStatus(String status) in C:\...\Splash.cs:line 395
       at UI.Menu.Main() in C:\...\Menu.cs:line 4275
  InnerException:

Someone built their own splash logic with multi-threading.

Funny that today, this got answered on StackOverflow by [WayBack] mgie: [WayBack] multithreading – TMonitor synchronization / Application.ProcessMessages – Stack Overflow.

Though that is a Delphi link (and points to the nice libraries [Archive.is] AsynCalls and [WayBack] OmniThreadLibrary), the most important link it contains is to  [WayBack] Borland Newsgroup Archive :: borland.public.delphi.internet.winsock :: Re: Disconnect TIdHttp in thread.

That sounds like a Delphi link too, but the subtitle “‘Ways to get into avoidable trouble with threads, V1.2′” hints the essence: it is a post that describes in an environment-agnostic way how to avoid multi-threading problems.

Recommended reading!

Anyway: Building multi-threaded code is hard. Even harder fleshing out all the corner cases and potential error conditions.

No matter what kind of programming environment: If you have not done lots of multi-threaded programming, then please don’t do it yourself: go ask someone that does know how to do it. Or better, try to avoid it.

I try to let libraries to the handling of multi-threading for me, if I use multi-threading at all, as others are far better at this than I am.

–jeroen

Posted in .NET, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Conference Topics, Conferences, Delphi, Development, Event, Java, Software Development, VB.NET, VBS, Visual Studio 2010, Visual Studio and tools, WinForms | 6 Comments »

.NET/C# – WinForms splash screen research material

Posted by jpluimers on 2012/06/21

I’m in the midst of converting a suite of WinForms C# projects from a range of .NET versions (1.x till 3.x) to 4 totalling some million lines of code.

One of the problems is that some people hacked together some splash screen stuff using multi-threading, doing all sorts of things that was forbidden in .NET 1 (and broke in .NET 2+).

On my research list for getting this to work:

  1. Mahin Gupta | Winforms splash screen – Great work by Tom. which is an update of
  2. A Pretty Good Splash Screen in C# – CodeProject.

–jeroen

Posted in .NET, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, Development, Software Development, Visual Studio 2002, Visual Studio 2003, Visual Studio 2005, Visual Studio 2008, Visual Studio 2010, Visual Studio and tools, WinForms | Leave a Comment »

.NET/C#: Using IDisposable to restore temporary settrings example: TemporaryCursor class

Posted by jpluimers on 2012/01/26

This is WinForms code from a long time ago, but the concept of using an IDisposable interface to do resource cleanup and restore a temporary setting is very valid.

You use the code below like this:

        private void myMethod()
        {
            // set busy cursor
            using (IDisposable waitCursor = new TemporaryCursor(this, System.Windows.Forms.Cursors.WaitCursor))
            {
                // logic that takes a long while
            }
        }

The code below implements the TemporaryCursor class; you can assign any System.Windows.Forms.Cursors item you want.

It restores the cursor upon these three “events”:

Most often the IDispose pattern is being used to make sure that resources get cleaned up. If you think of a wait cursor as a temporary resource, this example becomes much easier to remember.

Of course this is not limited to the System.Windows.Forms realm, you can just as well use this for non-visual temporaries, and other kinds of UIs like ASP.NET, WPF or SilverLight.

using System.Windows.Forms;

namespace bo.Windows.Forms
{
    public class TemporaryCursor : IDisposable
    {
        private Control targetControl;
        private Cursor savedCursor;
        private Cursor temporaryCursor;
        private bool disposed = false;

        public TemporaryCursor(Control targetControl, Cursor temporaryCursor)
        {
            if (null == targetControl)
                throw new ArgumentNullException("targetControl");
            if (null == temporaryCursor)
                throw new ArgumentNullException("temporaryCursor");
            this.targetControl = targetControl;
            this.temporaryCursor = temporaryCursor;
            savedCursor = targetControl.Cursor;
            targetControl.Cursor = temporaryCursor;
            targetControl.HandleDestroyed += new EventHandler(targetControl_HandleDestroyed);
        }

        void targetControl_HandleDestroyed(object sender, EventArgs e)
        {
            if (null != targetControl)
                if (!targetControl.RecreatingHandle)
                    targetControl = null;
        }

        // public so you can call it on the class instance as well as through IDisposable
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!disposed)
            {
                if (null != targetControl)
                {
                    targetControl.HandleDestroyed -= new EventHandler(targetControl_HandleDestroyed);
                    if (temporaryCursor == targetControl.Cursor)
                        targetControl.Cursor = savedCursor;
                    targetControl = null;
                }
                disposed = true;
            }
        }

        // Finalizer
        ~TemporaryCursor()
        {
            Dispose(false);
        }
    }
}

–jeroen

Posted in .NET, C#, C# 2.0, C# 3.0, C# 4.0, Development, Software Development, Visual Studio 2005, Visual Studio 2008, Visual Studio 2010, Visual Studio and tools, WinForms | 4 Comments »

c# – Panel.Dock Fill ignoring other Panel.Dock setting – Stack Overflow

Posted by jpluimers on 2011/11/08

Every once in a a while I do WinForms development. On the .NET platform it still is the best way to create simple business applications that just, well: work.

WinForms apps are not fancy, but the actual users don’t care much, as long as they can their daily work done. They love fanciness of their mobile devices, but for stuff they use 8 hours a day, they just want something that works quickly, well and easily. So WinForms for a baseline is good.

WinForms historically has had two ways of automatically: Anchors and Dock (.NET 2 introduced another way using FlowLayoutPanel and TableLayoutPanel, but often they make things more complicated than needed).

One of the pitfalls of Docking is when you set Dock to Fill. Sometimes the affected control will be too large.
Every time that happens, I am baffled, as .NET is the only platform with that behaviour; I use other platforms too, and they don’t have this docking peculiarity (of course the have others, that’s the fun of using multiple platforms <g>).

The solution is simple:

  1. Right click on the control that misbehaves
  2. Choose “Bring to Front”
Done :)

–jeroen

Via: c# – Panel.Dock Fill ignoring other Panel.Dock setting – Stack Overflow.

Posted in .NET, C#, C# 2.0, C# 3.0, C# 4.0, Development, Software Development, VB.NET, WinForms | 2 Comments »

.NET/C# WinForms: simple solution to Panel.Dock Fill ignoring other Panel.Dock setting – Stack Overflow

Posted by jpluimers on 2011/11/02

It has been a while, but I have done some WinForms maintenance on business apps. For those kinds of apps, WinForms still is a productive environment, apart from one thing:

When you have a Dock of Fill, sometimes that control fills more than it should.

The reason is the order in which things are being calculated.

I always forget the trick, as other very productive environments for writing business apps don’t have this peculiarity (they have others, life is full of interesting peculiarities <g>).

Simple solution:

  1. Right-Click on the control that has Dock=Fill
  2. Choose “Bring to Front”

Now it fills exactly the wanted area :)

Thanks Jeff Cuscutis for posting this concise solution.

–jeroen

Via: c# – Panel.Dock Fill ignoring other Panel.Dock setting – Stack Overflow.

Posted in .NET, Development, Software Development, WinForms | Leave a Comment »

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