C# Discussion Boards - CodeProject

21-Feb-06 4:50

I have a strange problem. Here is what I try to achieve:

Have a background thread performing work, and sending events so the form can update controls as work progresses. To do this, i use Delegate.BeginInvoke and its companion Delegate.EndInvoke.

This works very well, except when I added another event (still works for other events, though). This event is special as the it inform the Form that an exception has occured. This event has information to display to the user as how to fix the problem.

The EventArgs has a member similar to CancelEventArgs, to tell the event raiser whether the execution of the task should be retried or cancelled. To achieve this, the event handler displays a dialog box asking the user to fix the problem. This form has buttons to ask the user if the problem is fixed or not, thus indicating the worker thread to retry or not.

I have tried to display the secondary for to the user using 2 ways (none worked):

1- Calling Form.ShowDialog directly from the event handler.
2- Calling Form.Invoke from the event handler to have the secondary form instantiated on the same thread as the form one.

None work, the code stops at the Showdialog call, the form never appears, and the worker thread finishes at the event raising line (Delegate.EndInvoke is called).

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"I say no to drugs, but they don't listen."
- Marilyn Manson

Alvaro Mendez21-Feb-06 6:14

Alvaro Mendez

21-Feb-06 6:14

I tried something similar using an empty form, and it works fine. Are you sure your secondary isn't coming up behind your other windows? Smile | :)

I recommend you investigate the problem by simplifying it. Create a small app and focus on duplicating just the parts that you think are not working as expected.

Regards,
Alvaro

... now you see that evil will always triumph, because good is dumb. - Dark Helmet

Judah Gabriel Himango21-Feb-06 6:21

21-Feb-06 6:21

Sounds like the call to ShowDialog is on the wrong thread. Have you checked that with InvokeRequired?

As a side note, I highly recommend System.ComponentModel.BackgroundWorker for what you're doing. It handles exceptions for you, passing the exception as an object to an event raised on the UI thread. No manual Invoke/BeginInvoke required.

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Connor's Christmas Spectacular!
Judah Himango

Le centriste21-Feb-06 6:35

21-Feb-06 6:35

Unfortunately, I must use .NET 1.1. I will try the InvokeRequired.

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"I say no to drugs, but they don't listen."
- Marilyn Manson

Judah Gabriel Himango21-Feb-06 6:56

21-Feb-06 6:56

BAckgroundWorker for 1.1[^]

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Connor's Christmas Spectacular!
Judah Himango

Le centriste21-Feb-06 7:10

SOLVED (Unrelated to multithreading)

21-Feb-06 7:10

tx, interesting. Btw, the problem is fixed, I did set the Form.Enabled to false (typo in code, was supposed to be for anothe control).

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"I say no to drugs, but they don't listen."
- Marilyn Manson

Le centriste21-Feb-06 7:11

Array of pointers/references to another array

21-Feb-06 7:11

Form.Enabled was set to false. A mistake made selecting wrong item in Intellisense Mad | :mad:

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"I say no to drugs, but they don't listen."
- Marilyn Manson

naveed21-Feb-06 4:35

naveed

21-Feb-06 4:35

I have an array (List<t>) containing tens of thousands of items. I need to maintain copies of the array, sorted in a few different ways. I'm working on Windows Mobile so memory is a constraint. To minimize memory requirements, in C++, I can have arrays of pointers to the first array (T*[]). I understand I can do this in C# as well, but the code is unsafe. Is there a better way of doing this in C#

Le centriste21-Feb-06 4:53

21-Feb-06 4:53

This should work also, because objects variables are in fact references to instances of classes, not the instances themselves, thus all arrays have the same instance reference:

object o1 = new Object();

object[] oa1 = new object[] { o1 };
object[] oa2 = new object[] { o1 };

both arrays have reference to the exact same object.

--------

"I say no to drugs, but they don't listen."
- Marilyn Manson

naveed21-Feb-06 5:06

naveed

21-Feb-06 5:06

Thanks for your reply, Michel. Does it work the same way with the generic List as well?

Le centriste21-Feb-06 5:10

21-Feb-06 5:10

It works for all class types. struct types are passed by value, as well as primitive types

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"I say no to drugs, but they don't listen."
- Marilyn Manson

Windows Form from Outlook

naveed21-Feb-06 6:46

naveed

21-Feb-06 6:46

Thanks, just tested it and it works like you said.

<br />
namespace ListRef<br />
{<br />
	class Person<br />
	{<br />
		public string name;<br />
		public int id;<br />
<br />
		public Person(string name, int id)<br />
		{<br />
			this.name = name;<br />
			this.id = id;<br />
		}<br />
	}<br />
	<br />
	class Program<br />
	{<br />
		static void Print(List<Person> l, string s)<br />
		{<br />
			int i=0;<br />
			System.Console.WriteLine("\n --- {0}: --- ", s);<br />
			foreach(Person p in l)<br />
			{<br />
				System.Console.WriteLine("{0} {1} {2}", i, p.id, p.name);<br />
				i++;<br />
			}<br />
		}<br />
		<br />
		static void Main(string[] args)<br />
		{<br />
			List<Person> a = new List<Person>();<br />
			a.Add( new Person("jon", 1) );<br />
			a.Add( new Person("mary", 2) );<br />
			a.Add( new Person("hill", 3) );<br />
<br />
			List<Person> b = new List<Person>(a);<br />
			List<Person> c = new List<Person>();<br />
<br />
			Person[] x = new Person[] { new Person("abe", 5), new Person("jim", 6) };<br />
<br />
			a.AddRange(x);<br />
<br />
			c.AddRange(a);<br />
<br />
			Print(a, "a");<br />
			Print(b, "b");<br />
			Print(c, "c");<br />
<br />
			c[4].id = 555;<br />
<br />
			Print(a, "a");<br />
			Print(b, "b");<br />
			Print(c, "c");<br />
		}<br />
	}<br />
}<br />

tanishq151021-Feb-06 4:29

tanishq1510

21-Feb-06 4:29

Hi all,
I have an outlook addin which creates a Menubar in the Outlook explorer.There are 2 buttons in the explorer, when i click the buttons ,windows forms open. I have not faced any problem till this stage.But my problem arises when i try to move the form, i get distorted images of the form.Is there any way to avoid this.I have also tried making the outlook as parent form with the various APIs like SetWindowPos,ShowWindow etc.Your help is highly appreciated.
Thx in advance

Custom textbox with dropdownlist behavior

hansdredd21-Feb-06 4:28

hansdredd

21-Feb-06 4:28

Hi
I'm currently working on quite a big project and the need for a new custom control has come to our attention. What i´m looking for is a control that should be a combination of a textbox and a dropdownlist in the sense that i want to give the users the possibility to either select an item from the list or enter one themselves.

Is there such a control or does anyone have any ideas on how to make one..not new to custom controls just not keane on waisting time starting from scratch if someone allready knows of a good way..

Any ideas are helpful
Thanks Unsure | :~

Henrik

hooray21-Feb-06 5:18

hooray

21-Feb-06 5:18

Hey,

the standard ComboBox already has this functionality in .NET 2.0.
So there should be no reason to write a custom control for this behavior.

hansdredd21-Feb-06 20:25

hansdredd

21-Feb-06 20:25

To my knowledge i doesn't have it, but please let me know what properties in the
existing dropdownlist that set this behavior..

Henrik

Roy Heil22-Feb-06 7:46

Roy Heil

22-Feb-06 7:46

The standard ComboBox has always had this ability as long as Windows have had ComboBoxes. In fact, it is the default behavior.

The ComboBox has a property called DropDownStyle. Options are Simple, DropDown, and DropDownList. Simple makes it act like a TextBox, DropDownList restrict it to a DropDownList only (no typing in the box), and DropDown has both the Dropdown, and text edit.

Since you believe it is not already present, I wonder if what you really want is for the text entered by the user to be added to the dropdown list? If so, you would need to add code to do this. I would recommend having an "Add" button, which would add the value of ComboBox1.text to ComboBox1.items (with some code to make sure that the item is not already in the list).

Roy.

Why doesn't the compiler flag classes with public unlong-s as erroneous although the assembly is CLS compliant?

hansdredd23-Feb-06 20:52

hansdredd

23-Feb-06 20:52

Ok yeah that is true, sorry but i probably should have been more explicit in what i was looking for. What i forgot to mention is that i'm working on a web project so thats why i can't use the ComboBox youre suggesting. So what i'm looking for is a way to change a the webcontrol DropDownList to behave like a standard WinForm ComboBox.

Thanks for youre replies though. Smile | :)

Henrik

Vikram A Punathambekar21-Feb-06 3:53

Vikram A Punathambekar

21-Feb-06 3:53

I read that ulong is not CLS compliant, but this code compiles cleanly on .NET 2.0. Any idea why? Was my source wrong?

using System;

[assembly:CLSCompliant(true)]

namespace CustomAttributes
{
	[CLSCompliant(true)]
	public class MarutiZen
	{
		decimal price;
		public ulong MyULong;

		public MarutiZen()
		{
		}
	}
}

Thanks in advance. Smile | :)

Cheers,
Vikram.

"When I read in books about a "base class", I figured this was the class that was at the bottom of the inheritence tree. It's the "base", right? Like the base of a pyramid." - Marc Clifton.

Re: Why doesn't the compiler flag classes with public unlong-s as erroneous although the assembly is CLS compliant?

Judah Gabriel Himango21-Feb-06 6:30

Re: Why doesn't the compiler flag classes with public unlong-s as erroneous although the assembly is CLS compliant?

21-Feb-06 6:30

Vikram A Punathambekar wrote:
using System;[assembly:CLSCompliant(true)]namespace CustomAttributes{ [CLSCompliant(true)] public class MarutiZen { decimal price; public ulong MyULong; public MarutiZen() { } }}

I get a compiler warning saying, "Type of 'TestingApp.Form1.MarutiZen.MyULong' is not CLS-compliant".

Vikram A Punathambekar21-Feb-06 16:31

Vikram A Punathambekar

21-Feb-06 16:31

Thanks, Judah. Ok, I didn't look carefully enough. There's indeed a warning, but the documentation says I should get an error. Confused | :confused:

Cheers,
Vikram.

"When I read in books about a "base class", I figured this was the class that was at the bottom of the inheritence tree. It's the "base", right? Like the base of a pyramid." - Marc Clifton.

Re: Why doesn't the compiler flag classes with public unlong-s as erroneous although the assembly is CLS compliant?

Judah Gabriel Himango21-Feb-06 17:12