C# threads and invoking - C# Discussion Boards

Re: OutOfMemoryException

harold aptroot2-Jul-09 11:38

harold aptroot

2-Jul-09 11:38

qwerty53 wrote:
any thoughts?

* Just because the exception is thown there doesn't mean the problem is there - but usually it is anyway.
* String concatenation is "dangerous" for memory usage, I would definitely check that to make sure you aren't somehow making a string of millions of characters long.
* I have a feeling that you're concatting strings in the delegate that you pass to Invoke but that's just a feeling..

Just thoughts, that's where you asked for anyway. But unless you answer some of the questions asked by other, you're not likely to get much more than thoughts and insults.

MSChart RangeColumn type chart [modified]

JohnQuar12-Jul-09 7:23

JohnQuar1

2-Jul-09 7:23

Hello,
I am trying to create a RangeColumn chart in Visual Studio 2008 with C#. All of my data is being brought in through a DB and is fairly simple.

I have two columns, a category and a value.

I want the first category to be displayed normally with y= 0 and then go to y= 200. Then I want the second category to start at y=200 then go to y=300, so basically it would not be starting at zero anymore. Ive heard this referred to as a waterfall chart, but not entirely sure.

I do not how to do this with just two columns of data. Do I need to create a query that does all of the math or is there a way do to this through the properties in MSChart?

Data

Category		Total
Device		38111
Plant		6063
Improvement		2266

ex
DEVICES: x=0, y1= 0, y2= 38111
PLANT: x=1, y1= 38111, y2 = 44174
IMPROVEMENTS: x=2, y1= 44174, y2 = 46440

I have been making all of the charts entirely through the design mode of Visual Studio 2008, and have not played with the code at all.

I would be forever indebt to you if you could help out. Thanks!

JM

modified on Thursday, July 2, 2009 1:45 PM

hi friends

jeyaluxmy2-Jul-09 6:17

jeyaluxmy

2-Jul-09 6:17

i want to do one project in AForge.Net. my project is when a person infront of the web cam, it should capture the image and identify the eye part only. then when that person close his eye it should says a message eye closed. please help me as soon as possible.
thank u soo much

Re: hi friends

Rajesh R Subramanian2-Jul-09 6:27

Rajesh R Subramanian

2-Jul-09 6:27

See points: 1, 2, 3, 4 and 9 in this post[^]

It is a crappy thing, but it's life -^ Carlo Pallini

Re: hi friends

led mike2-Jul-09 6:37

led mike

2-Jul-09 6:37

jeyaluxmy wrote:
please help me as soon as possible.

I think you are looking for this site[^]

Re: hi friends

Henry Minute2-Jul-09 6:40

Henry Minute

2-Jul-09 6:40

Well, you ain't never caught a rabbit, and you ain't no friend of mine. Smile | :)

Henry Minute

Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”

Re: hi friends

musefan2-Jul-09 6:48

musefan

2-Jul-09 6:48

Did you know you have accidentally used the question icon instead of the 'joke' message type.
Laugh | :laugh:

Life goes very fast. Tomorrow, today is already yesterday.

C# threads and invoking

Blue3652-Jul-09 6:15

Blue365

2-Jul-09 6:15

Hi all,

I am trying to invoke the forms main thread from a worker thred, but I am desperately trying to avoid Control.InvokeRequired. To better explain, here is the code:

Simple class: (MyClass.cs)

public class MyClass
{
   public delegate void LiveStatsLoginRequest(object sender, LiveStatsLoginEventArgs e);
   public event LiveStatsLoginRequest OnLSLoginRequest;

   public MyClass()
   {

   }

   public void OpenConnection(string postData)
   { 
      var args = new object[] {postData, Operation.Check, LiveStatsAction.Authenticate};
      var t = new Thread(dowork);
      t.Start(args);
   }

   private void dowork(object args)
   {
      DoSomethingThatTakesALongTime();
      OnLSLoginRequest.Invoke(this, new EventArgs());
   }
}

Now the main form (MainForm.cs)

public partial class MainForm : Form
{
   private MyClass myClass;

   public MainForm()
   {
      InitializeComponent();
      myClass = new MyClass();
      MyClass.OnLSLoginRequest += LiveStats_OnLSLoginRequest;
   }

   private void Form_Load(object sender, EventArgs e)
   {
      myClass.OpenConnection(new object[]{"Something"};
   }

   private void LiveStats_OnLSLoginRequest(object sender, LiveStatsLoginEventArgs e)
   {
       this.TextBox1.Text = "Logged in!";
   }
}

The problem is that I get an error due to cross threading. I know that I can fix this my doing the following:

MainForm.cs

private void LiveStats_OnLSLoginRequest(object sender, LiveStatsLoginEventArgs e)
{
    if (InvokeRequired)
    {
        //do invoke
    }
    else
    {
        this.TextBox1.Text = "Logged in!";
    }
}

But I think this is messy and I would like to do the invoking through the class itself. I will eventually be releasing this code open source and don't want the user to have to worry/need to invoke the main form.

How can I solve this?

many thanks

(Sorry for the crude code!)

Bluetooth Marketing|Bluetooth Advertising

Re: C# threads and invoking

Henry Minute2-Jul-09 6:44

Henry Minute

2-Jul-09 6:44

Take a look at Avoiding InvokeRequired[^] and see if that helps.

Re: C# threads and invoking

Luc Pattyn2-Jul-09 6:50

Luc Pattyn

2-Jul-09 6:50

The spell clearly didn't work in my favor, now you're beating me in answering C# questions Confused | :confused:

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

modified on Thursday, July 2, 2009 1:03 PM

Re: C# threads and invoking

Henry Minute2-Jul-09 6:56

Henry Minute

2-Jul-09 6:56

How does it go?
Zut alors! Big Grin | :-D

Re: C# threads and invoking

Luc Pattyn2-Jul-09 6:49

Luc Pattyn

2-Jul-09 6:49

Hi,

Control.InvokeRequired is the correct way to deal with this.

You can hide it in a helper class, that is what Avoiding InvokeRequired[^] (a very recent article here on CP) does for you, however I'd rather use code that works straight with InvokeRequired.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Re: C# threads and invoking

Blue3652-Jul-09 12:22

Blue365

2-Jul-09 12:22

Luc Pattyn wrote:

You can hide it in a helper class, that is what Avoiding InvokeRequired[^] (a very recent article here on CP) does for you, however I'd rather use code that works straight with InvokeRequired.

Hmm I see what you mean (i sorta missed what you said when i first read your post). I read this article and have spent the last couple of hours playing with the demo. It really does just move the problem. May be better tools for this problem should be added to .NET 4.0 (hell its bloated anyway).

I dont know if its the intense heat (some 30C here in the UK), the fact that I am tired, or the fact that I'm watching family guy marathon on DVD, but ive taken the easy way out.

First in MyClass.cs I have added the following property:

public Form Sender { get; set; }

now when a method is called, just before an event is raised, the sender form is checked for InvokeRequired.

if (Sender.InvokeRequired)
{
    var dataDelegate = new Data(LiveStats_OnData);
    Sender.Invoke(dataDelegate, new object[]{sender,e});
}
else
{
    //raise event
}

the horrible nasty InvokeRequired is now tucked away and abstract so the user never sees it.

Bailed. Please Microsoft, give us a break.

Bluetooth Marketing|Bluetooth Advertising

Re: C# threads and invoking

Luc Pattyn2-Jul-09 12:53

Luc Pattyn

2-Jul-09 12:53

Hi,

I'm not convinced you need to go for all that sender trouble: when all Controls got created by the main thread (that's the safest way to do WinForms) then whatever Control you ask for InvokeRequired will return the same value: false on the main thread, true otherwise. So a single Form or Control is all you need (and then you could also use the context stuff, which I haven't used yet).

PS: it's the same 30C in B.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Re: C# threads and invoking

Alan N2-Jul-09 8:29

Alan N

2-Jul-09 8:29

Hi,
The System.ComponentModel.BackgroundWorker class raises it’s events on UI thread and would suit your requirements as you only require a task completed event.

In general terms it is possible to arrange for an event to be raised on the UI thread through use of either the Post or Send methods of the SynchronizationContext class or alternatively the Post method of the AsyncOperation class.

I’ve pasted in an example class that shows one way of doing this.

Alan.

using System;
using System.ComponentModel;
using System.Threading;
public class BackGroundTask {
  private SynchronizationContext context;
  public event EventHandler<AsyncCompletedEventArgs> Completed;

  /// <summary>
  /// Start the background task
  /// </summary>
  public void RunAsync(Object args) {
    this.context = AsyncOperationManager.SynchronizationContext;
    ThreadPool.QueueUserWorkItem(new WaitCallback(this.ThreadProc), args);
  }

  private void ThreadProc(Object args) {
    Exception exc = null;
    Boolean cancelled = false;
    try {
      ////this.DoWork();
    } catch (Exception e) {
      exc = e;
    } finally {
      this.OnCompleted(exc, cancelled, null);
      this.context = null;
    }
  }

  private void OnCompleted(Exception e, Boolean cancelled, Object state) {
    // Using anonymous delegate to allow access to local variables
    this.context.Post(
      delegate {
        EventHandler<AsyncCompletedEventArgs> handler = this.Completed;
        if (handler != null) {
          AsyncCompletedEventArgs args = new AsyncCompletedEventArgs(e, cancelled, state);
          handler(this, args);
        }
      },
    null);
  }
}

GridView and making my site look like this page

mjc2252-Jul-09 6:12

mjc225

2-Jul-09 6:12

I love the way these pages look. How you have a list of all the posts, can click on one, and the whole post is displayed. I am in the process of doing something similar. I'm building a website that will show 5 of say 17 fields from a selected record in GridView kind of like to get the user's attention. Then, when the user clicks any of the 5 fields, all 17 fields would drop down, much like this page. Can that be done only with GridView or would I have to add a View/MultiView to the page. If I can do it with GridView is there a property I can set or would I have to write custom code? Are there any good code snippets out there?
THanks.

Re: GridView and making my site look like this page

Moim Hossain2-Jul-09 9:30

Moim Hossain

2-Jul-09 9:30

mjc225 wrote:
If I can do it with GridView is there a property I can set or would I have to write custom code?

I believe that you've to write custom code.

Moim Hossain
R&D Project Manager
BlueCielo ECM Solutions BV

Enumerate Custom Class

Dowse2-Jul-09 4:40

Dowse

2-Jul-09 4:40

Hi all

Have started writing a Class to help me with a problem in my current project and I would like to be able enumerate the variables in the Class by using a 'foreach(object o in MyClass)' in my main program.

I was getting a 'MyClass does not contain a public definition for GetEnumerator' but have worked out why and I am at the point where I could really do with some help with the GetEnumerator function.

public class MyClass : IEnumerable
{
    public System.DateTime datStart;        //Schedule start date
    public System.DateTime datEnd;          //Date of final occurrence (#1/1/1900# if N/A)
    public int intParam1;                   //Various Uses
    public int intParam2;                   //Various Uses
    //Other fields remove for clarity

    //Constructor
    public MyClass()
    {
        //Set defaults for new MyClass()
        datStart = new DateTime(1900, 1, 1);
        datEnd = datStart;
        intParam1 = -1;
        intParam2 = -1;
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        //What goes here?

        return null;  //Only added this line to stop compiler error
    }
}

I know there are many, (many, many,) references to this on the web but I haven't been able to re-work any of them to solve my specific problem.

Any help would be MUCH appreciated.

Thank you.

Re: Enumerate Custom Class

Thomas Weller2-Jul-09 5:36

Thomas Weller

2-Jul-09 5:36

You seem to misunderstand the concept of enumerators:
You don't enumerate a single class, but you enumerate over collections like e.g. List or Dictionary.
Not quite sure what you are trying to do, but IEnumerable is definitely not the way...

Regards
Thomas

www.thomas-weller.de

Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
Programmer - an organism that turns coffee into software.

Re: Enumerate Custom Class

Dowse2-Jul-09 5:45

Dowse

2-Jul-09 5:45

Thomas

Thank you for taking the time to reply to my post.

I am trying to implement foreach(object o in MyClass) for reporting and (possibly) serialization.

Re: Enumerate Custom Class

Thomas Weller2-Jul-09 6:07

Thomas Weller

2-Jul-09 6:07

You could use reflection to enumerate over all the desired members of a class - like described in the post below. Alternatively simply implement a method object[] GetAllObjects() that returns everything you need. For serialization use the Serializable attribute and eventually the ISerializable interface (see here^ and here^).

Regards
Thomas

Re: Enumerate Custom Class

Dowse2-Jul-09 6:10

Dowse

2-Jul-09 6:10

Thomas

I will read up on reflection. It seems to be what I was after.

Thank you.

Re: Enumerate Custom Class

Luc Pattyn2-Jul-09 5:47

Luc Pattyn

2-Jul-09 5:47

Hi,

As Thomas said enumerators is not what you need here.
You need Reflection, which can give you access to all the data fields, constructors, methods, properties of your class.

This is an example listing all the known colors in the SystemColors class:

Assembly asm=Assembly.GetAssembly(Color.White.GetType());
Type type=asm.GetType("System.Drawing.SystemColors", true);
PropertyInfo[] pis=type.GetProperties();
int n=pis.Length;
log("There are "+n+" properties");
foreach (PropertyInfo pi in pis) {
    Color c=(Color)pi.GetValue(null, null); // get the SystemColor
    log(pi.Name+" = "+c.ToString());
}

BTW: you can only get information on class members, not on local variables inside some method.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Re: Enumerate Custom Class

Dowse2-Jul-09 6:03

Dowse

2-Jul-09 6:03

Thank to all that responded to my post.

Luc, I think I can re-work your example to give me what I was after.

Thank you.

Re: Enumerate Custom Class

Dowse2-Jul-09 7:01

Dowse

2-Jul-09 7:01

Luc, I managed to re-work your example to give me just what I was after.

Thanks for putting me on the right track:

private void ShowData()
        {
            Type type = typeof(MyClass);
            FieldInfo[] fi = type.GetFields();

            foreach (FieldInfo info in fi)
            {
                Debug.WriteLine(info.Name + " = " + info.GetValue(varMyClass));
            }
        }

varMyClass is a variable of type MyClass.

Thanks to all who helped.

modified on Thursday, July 2, 2009 1:41 PM

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