Variable assignment problem... - C# Discussion Boards

Re: Threads and exceptions

11-Feb-05 7:16

When a thread is started and it throws an exception, where is it thrown? More specifically, I need the calling function to somehow know what has happened (success or failure).

How can I do this?

Thanks,
Jim

Robert Rohde11-Feb-05 7:46

Robert Rohde

11-Feb-05 7:46

You will have to catch the exception in the thread where it occurs. The is nor direct way to cacth the exception in the function which created the thread.
One possibility would be to cacth the exception in the thread in set some property where the calling function get check if and what kind of exception occured in the thread.

Re: Threads and exceptions

Esmo200011-Feb-05 7:59

Re: Threads and exceptions

11-Feb-05 7:59

Thats a shame, there really should be a better way to do that. Is that how its usually done?

Cheers,
Jim

Daniel Turini11-Feb-05 8:17

Daniel Turini

11-Feb-05 8:17

I just posted an article that may help you:
Exception Handling Best Practices in .NET[^]

Yes, even I am blogging now!

Asynchronous message processing

Esmo200011-Feb-05 4:55

Re: Asynchronous message processing

11-Feb-05 4:55

I have a method that is picking up messages off of a MSMQ. In the function, I want to tell it to block the thread until the next message comes in. Previously I had

// start looking for the next message
IAsyncResult AsyncResult = ((MessageQueue)e.AsyncResult.AsyncState).BeginReceive(
new TimeSpan(1, 0, 0), ((MessageQueue)e.AsyncResult.AsyncState));

But this is time based. I want to do this indefinitely. When I tried

MQ.receive();

it works fine but it does not pick up the next message. Why?

Thanks a lot,
Jim

Esmo200011-Feb-05 7:15

Variable assignment problem...

11-Feb-05 7:15

Ah, I figured it out. Your supposed to use beginReceive() Perhaps what I was using was for transactional code or something.

Cheers,
Jim

new_phoenix11-Feb-05 4:32

new_phoenix

11-Feb-05 4:32

Having a bit of a tricky problem with the contention for the assignment of the value to a variable. I would like the variable to be assigned in two ways both in the onLoad event. If the user clicks on a menu item, then it becomes checked and assigns the value based upon which of the appropriate menu items is selected. However, if the user does not select a menu item, the value is assigned based upon the application settings (as stored in an XSD/XML initialization file) when the application is opened. The question is this - how do I differentiate between whether the user has selected a MenuItem from the menu or if the user has only opened the application anew without making such a selection?

If the menu item is selected, assign the variable based upon the menu item (the assignment variable currently works), and if the user does not make such a selection, then use the XSD/XML file to assign the variable.

Example:

<br />
private void onLoad(object sender, System.EventArgs e)<br />
{<br />
   if ((mnuItem1.clicked) || (mnuItem2.clicked) ||<br />
     (mnunItem3.clicked) || (mnuItem4.clicked))<br />
   {<br />
      strVariable = [value from menu item]<br />
   }<br />
   else<br />
   {<br />
      strVariable = [value from XSD/XML initialization file]<br />
   }<br />
}<br />

Alternatively:

<br />
private void onLoad(object sender, System.EventArgs e)<br />
{<br />
   if ((MenuItem)sender).Name == "mnuItem1") || <br />
      (MenuItem)sender).Name == "mnuItem2") ||<br />
      (MenuItem)sender).Name == "mnuItem3") ||<br />
      (MenuItem)sender).Name == "mnuItem4"))<br />
   {<br />
      strVariable = [value from menu item]<br />
   }<br />
   else<br />
   {<br />
      strVariable = [value from XSD/XML initialization file]<br />
   }<br />
}<br />

Neither of the above code segments works because there is neither a .clicked nor a .name property for the MenuItem class. The code should be processed based upon whether the user selects the menu item or if the user does nothing and just allows their application settings to reload into the variable. How do I check to see whether the user made the selection from the menu, or is merely opening the application? Would really appreciate the assistance! Confused | :confused:

Re: Variable assignment problem...

Daniel Turini11-Feb-05 6:53

Daniel Turini

11-Feb-05 6:53

Instead of this:

new_phoenix wrote:
if ((MenuItem)sender).Name == "mnuItem1") ||
(MenuItem)sender).Name == "mnuItem2") ||
(MenuItem)sender).Name == "mnuItem3") ||
(MenuItem)sender).Name == "mnuItem4"))
{

Try this:

if ((MenuItem)sender) == mnuItem1) ||
(MenuItem)sender) == mnuItem2) ||
(MenuItem)sender) == mnuItem3) ||
(MenuItem)sender) == mnuItem4))

There's no need to compare a property: you can always compare the reference and see if they are the same object.

Yes, even I am blogging now!

Re: Variable assignment problem...

new_phoenix11-Feb-05 9:01

new_phoenix

11-Feb-05 9:01

Daniel Turini:

D'Oh! | :doh:

I just had a Homer Simpson moment when I realized that a menu selection does not return a value to the onLoad event. Thus, I developed a potential workaround solution. Tell me if you think that this is a viable alternative. I have coded it, but I have not yet tested it.

If I were to put a protected string variable in the variables section of the form and assign it to String.Empty, and then I assigned that string variable in each of the menu selection items, and then in the onLoad event checked to see if that variable was empty or not. Presume that the menu selection reloads the onLoad event. If not empty, then it must have been a menu selection, so the variable could be processed that way. If the variable is empty, then the user must have just started to run the program because the variable was assigned during initialization to String.Empty. Tell me, do you think that this approach would work?

As usual, I appreciate all input and detailed explanations about alternative courses of action. All insights are valuable and appreciated !!!

Thanks, Daniel Turini

TaskbarNotification display problems

eynkram11-Feb-05 4:27

eynkram

11-Feb-05 4:27

Hi,
I recently downloaded the code from a project on this site called TaskbarNotification. It is a little msn style popup window that pops up on the taskbar. When using this class in a single threaded application it works fine. Now i have to use multi-threading because the program checks a mysql database for updates and pop's up the window when there is one. Since i need to loop indefinatly I had to thread the task. Now a line only appears at the bottom of the taskbar and goes away. If I add a call to MessageBox.Show("whatever") write after i call taskbarNotification1.show() the message box pops up and the taskbar notification window shows. I thought the problem could be the passing of the background bitmap to the taskbarNofication class. I tried to initialize the background bitmap in the actual class but get a resource error. I guess threads don't have access to the resources the Microsoft Studio makes you add. Any help would be appreciated..

Thanks..
Mark

Re: TaskbarNotification display problems

eynkram17-Feb-05 3:52

eynkram

17-Feb-05 3:52

Hi All,
This ones a stumper.... Some more detail..

The thread gets started that loops indefinately. It checks a database for a new message and displays it in the taskbar popup window. In the thread class i created there is a block of code initializing the popup window. When you call the show function:

taskbarNotifier1.Show("Chatter",what,500,5000,200);

You get a small line on top of the taskbar. If I change the code to this..

taskbarNotifier1.Show("Chatter",what,500,5000,200);
MessageBox.Show(what);

The popup window shows as long as the messagebox is open. When I close the messagebox the popup disapears.

This is very strange almost bug like.

Does anyone have any suggestions or thoughts on this.. Please help!!!

Thanks,
Mark

Problem while Working with XmlValidatingReader!!!!!

abcxyz8211-Feb-05 4:01

abcxyz82

11-Feb-05 4:01

I am experimenting with "XmlValidatingReader" and want to create a event handler which gets called there occurs some validation error(schema mismatch etc..) But could not find where this class is located??

I am using .NET framework 2.0, VS 2005 beta1..

Is there any other way to validate xml with schema?

REgards.
MaulikCE

Re: Problem while Working with XmlValidatingReader!!!!!

Phil Hobgen11-Feb-05 22:53

Phil Hobgen

11-Feb-05 22:53

Hi,

The XmlValidatingReader class is obsolete in v2.0.

You can read about validating xml in v2.0 here:
http://msdn2.microsoft.com/library/hdf992b8.aspx[^]

Cheers

Phil Hobgen
barbari.co.uk
Southampton, UK

AppDomain and ResolveEventArgs

Marc Clifton11-Feb-05 3:24

Marc Clifton

11-Feb-05 3:24

Why is it, that when I create a new AppDomain and attempt to load an assembly into it, I get "ResolveEventArgs is not marked as Serializable"?

I mean, duh, it's not marked Serializable. How do I work around this problem?

It seems that the .NET implementation prevents you from using the AssemblyResolve event in a new AppDomain. Is this true? Is there a better way that would actually work?

Thanks!

Marc

MyXaml
Advanced Unit Testing
YAPO

Re: AppDomain and ResolveEventArgs

Daniel Turini11-Feb-05 7:01

Daniel Turini

11-Feb-05 7:01

Marc Clifton wrote:
It seems that the .NET implementation prevents you from using the AssemblyResolve event in a new AppDomain. Is this true? Is there a better way that would actually work?

The .NET framework is trying to serialize a ResolveEventArgs because it's trying to make a call that crosses domains. Are you capturing the AssemblyResolve event on the newly created AppDomain? If so, you should do so from the loaded assembly only, so the call does not cross domains.
I'm not sure that this explanation was clear enough... Unsure | :~

Yes, even I am blogging now!

Re: AppDomain and ResolveEventArgs

leppie11-Feb-05 9:45

leppie

11-Feb-05 9:45

I suggest you handle the event in the AppDomain itself, and then exposing it with you own (serializable) event, if thats possible...

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Download xacc-ide 0.0.3 now!
See some screenshots}

automatic scroll down in rich text box

kitsune_me11-Feb-05 2:57

11-Feb-05 2:57

does anyone know how to automate the scrolling down to the bottom of rich text box and the scroll bar everytime a new string has been appended?

leppie11-Feb-05 3:08

leppie

11-Feb-05 3:08

class RichTextBox : System.Windows.Forms.RichTextBox
{
  void ScrollToEnd()
  {
    Point pt2 = GetPositionFromCharIndex(0);
    Point pt = GetPositionFromCharIndex(TextLength);
    const int msg = 0x400 + 222;
    Point point = new Point(0, Font.Height + pt.Y - pt2.Y - Height);
    SendMessage(Handle, msg, 0, ref point);
  }

  [DllImport("user32.dll")]
  extern static int SendMessage(IntPtr hwnd, int id, int res, ref Point pos);

  protected override void OnSizeChanged(EventArgs e)
  {
    ScrollToEnd();
    base.OnSizeChanged (e);
  }

  //this scrolls the text to the last line when ever text is changed.
  protected override void OnTextChanged(EventArgs e)
  {
    ScrollToEnd();
    base.OnTextChanged (e);
  }
}

^{top secret
Download xacc-ide 0.0.3 now!
See some screenshots}

kitsune_me11-Feb-05 18:27

11-Feb-05 18:27

thank you.

mav.northwind11-Feb-05 4:36

mav.northwind

11-Feb-05 4:36

It should be possible without P/Invoke as well:
After appending a string call this:

richTextBox1.Select(richTextBox1.Text.Length, 0);
richTextBox1.ScrollToCaret();

Regards,
mav

kitsune_me11-Feb-05 5:25

11-Feb-05 5:25

is there any other way? it doesnot seem to work. the rich text box still does not automatically scroll down. as well as the scroll bar thanks

mav.northwind11-Feb-05 6:07

mav.northwind

11-Feb-05 6:07

You're right, it _should_ work (as I wrote), but unfortunately doesn't. Frown | :(

There's a bug in the .NET RichTextBox that prevents ScrollToCaret() from working when the RichTextBox doesn't have Focus.

If you add the line

richTextBox1.Focus();

before the call to ScrollToCaret() it'll work (I've tried it this time Smile | :)

).

mav

Dave Kreskowiak11-Feb-05 9:13

Dave Kreskowiak

11-Feb-05 9:13

It's not a bug. It's documented in the TextBoxBase class that TextBox and RichTextBox inherit from. In order for ScrollToCaret to work, the control must have the focus.

Remarks<br />
This method enables you to scroll the contents of the control until the caret is within the visibile region of the control. If the caret is positioned below the visible region of the control, the ScrollToCaret method will scroll the contents of the control until the caret is visible at the bottom of the control. If the caret is positioned above the visible region of the control, this method scrolls the contents of the control until the caret is visible at the top of the control. You can use this method in a multiline text box to ensure that the current text entry point is within the visible region of the control.<br />
<br />
Note   This method has no effect if the control does not have focus or if the caret is already positioned in the visible region of the control.<br />

Docs on TextBoxBase.ScrollToCaret Method[^]

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

kitsune_me11-Feb-05 18:26