C# Discussion Boards - CodeProject

Ben Fair28-Dec-09 2:52

28-Dec-09 2:52

Yes, Microsoft purposely made the String type act like a value type, even though it is really a reference type; it is immutable. Any operations on a String produce a copy, or a partial copy, of the String; the underlying string data cannot be directly changed. This is why you have to do a = a.ToUpper(); in the first place, rather than the ToUpper() method directly changing the String. This is also the reason that the StringBuilder class exists, because it allows string manipulation without the extra copying, and thus has better performance in situations where lots of string manipulation will be happening.

Re: A simple question regarding String

harold aptroot26-Dec-09 6:21

harold aptroot

26-Dec-09 6:21

Because it's not a.ToUpper() but a = a.ToUpper() - ToUpper doesn't change anything, it returns a new string.
If you change the actual string (yes you can, unsafe code), b should probably change

Re: A simple question regarding String

uusheikh26-Dec-09 23:01

uusheikh

26-Dec-09 23:01

Ok, i understand. Thanks.

Custom item list

Zaegra26-Dec-09 2:32

Zaegra

26-Dec-09 2:32

Hi,

I was wondering:
I have an user-control called myUserControl. This control contains items, say myUserControlItems. Now I want to add a property to myUserControl, which contains a list of myUserControlItems.

So:

myUserControl usrctrl = new myUserControl();
myUserControlItem usritem = new myUserControlItem();
myUserControl.Items.Add(usritem);

I can accomplish this by setting the type of the property to myUserControlItem[], but this isn't as dynamic as e.g Listviewitems in a ListView.

Can somebody help me out on this one?

Greets,
Zaegra

Motivation is the key to software development.

Re: Custom item list

Abhinav S26-Dec-09 2:36

Abhinav S

26-Dec-09 2:36

A property of type List<myUserControlItem> may suite your needs.

There's nothing left in my right brain and nothing right in my left brain.

Re: Custom item list

Jimmanuel26-Dec-09 2:40

Jimmanuel

26-Dec-09 2:40

use a list instead of an array:

List<myUserControlItem> abc = new List<myUserControlItem>();

myUserControlItem usritem = new myUserControlItem();
abc.Add(usritem);

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Re: Custom item list

Luc Pattyn26-Dec-09 3:02

Luc Pattyn

26-Dec-09 3:02

Zaegra wrote:
Custom item list

you call it a list, yet you don't use a List<>?

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Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Re: Custom item list

Zaegra26-Dec-09 3:18

Zaegra

26-Dec-09 3:18

Motivation is the key to software development.

Delete Drawed Shape

dataminers25-Dec-09 23:34

dataminers

25-Dec-09 23:34

I draw circle and line to windows form using with GDI.

Sample code;

Graphics graph = this.CreateGraphics();
graph.DrawArc(Pen.Red, new Rectangle(pFisrtPoint, new Size(pSecondPoint.X - pFirstPoint.X, pSecondPoint.Y - pFirstPoint.Y)), 0, 360);

Graphics graph = this.CreateGraphics();
graph.DrawLine(Pen.Red, pFirstPoint, pSecondPoint);

How can I delete shape when just mouse hover this shape painted area area?

Best Regards...

Re: Delete Drawed Shape

Luc Pattyn26-Dec-09 1:47

Luc Pattyn

26-Dec-09 1:47

Hi,

This[^] explains how you should go about it.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Re: Delete Drawed Shape

dataminers29-Dec-09 22:38

dataminers

29-Dec-09 22:38

This article is not related about my problem. Do you have any idea? Thanks...

Re: Delete Drawed Shape

Luc Pattyn30-Dec-09 0:33

Luc Pattyn

30-Dec-09 0:33

yes it is, each time your drawing has to change, change the data and call Invalidate().

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

unsafe

sanforjackass25-Dec-09 22:38

sanforjackass

25-Dec-09 22:38

how can i use unsafe code?

Re: unsafe

dan!sh 25-Dec-09 22:44

dan!sh

25-Dec-09 22:44

You can create a unsafe code block using unsafe keyword and place all of your unsafe code inside it.

50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong...!!

Re: unsafe

sanforjackass25-Dec-09 22:53

sanforjackass

25-Dec-09 22:53

i have code that use unsafe code but when i debug it an error "unsafe code may only appear if compiling with /unsafe"
what can i do?

Re: unsafe

dan!sh 25-Dec-09 23:00

dan!sh

25-Dec-09 23:00

Go to project properties. There, under Build tab, check allow unsafe code checkbox.

50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong...!!

Re: unsafe

sanforjackass25-Dec-09 23:44

sanforjackass

25-Dec-09 23:44

thanks alot Thumbs Up | :thumbsup:

types formats in app.config

Hussam Fattahi25-Dec-09 22:21

Hussam Fattahi

25-Dec-09 22:21

after serching in msdn and internt i couldn't find any predefined section in application config file
to save the types formats (( shor or long for dates etc..))

is there such an element or cofiguration section to save this information
or do i have to create a custom configuration section for it

thanks

Re: types formats in app.config

dan!sh 25-Dec-09 22:42

dan!sh

25-Dec-09 22:42

You can add a key under appsettings for the date format and then access it in the code using ConfigurationSettings.AppSettings["dateFormatKey"].ToString().

50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong...!!

Aborting a Thread.

Ronni Marker25-Dec-09 22:12

Ronni Marker

25-Dec-09 22:12

Hi I have the following code that is updating an dropdown box with information Active Directory information - this below will show Domain Controllers btw.

But I am trying unsuccessfully to cancel an existing running thread if one exist already. this is mainly because sometimes a thread can be running indefinitely and need to abort that, or if another thread is called that need to update the same dropdownbox. Anyway are there any out here who could explain how I could abort an running thread?

private void ThreadDC()
{

    Thread TRDomainC = new Thread(ThreadingDC);
    if (TRDomainC.IsAlive)
    {
        TRDomainC.Abort();
    }
    TRDomainC.SetApartmentState(ApartmentState.STA);
    TRDomainC.Start();
}

private void ThreadingDC()
{
    comboBox1.Items.Clear();
    try
    {
        if (comboBoxDomains.SelectedIndex >= 0 && comboBoxDomains.SelectedIndex != -1)
        {
            foreach (string dc in domainInfoComponent[comboBoxDomains.SelectedItem.ToString()])
            {
                comboBox1.Items.Add(dc);
            }
            lastIndex = comboBoxDomains.SelectedIndex;
            comboBox1.SelectedIndex = 0;
        }
    }
    catch
    {
        lastIndex = 0;
        comboBox1.SelectedIndex = -1;
    }
}

Re: Aborting a Thread.

Nicholas Butler25-Dec-09 22:46

Nicholas Butler

25-Dec-09 22:46

Don't use Thread.Abort - it's evil!

If you want to end a thread, do it cooperatively - make the thread return from it's main method and it will be cleared up properly.

Also, you cannot touch UI controls from any thread other than your main UI thread. Control.Invoke is helpful here.

Here is a good introduction to threading: http://www.albahari.com/threading/[^]

Nick

----------------------------------
Be excellent to each other Smile | :)

Re: Aborting a Thread.

Ronni Marker26-Dec-09 2:30

Ronni Marker

26-Dec-09 2:30

Not really an option waiting. So need to kill the thread one way or another.

I know about Control.Invoke, but well, dosn't really help me on ending the thread before it is completed.

Ronni

Re: Aborting a Thread.

Luc Pattyn26-Dec-09 1:50

Luc Pattyn

26-Dec-09 1:50

As Nick said; this[^] may help also.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Re: Aborting a Thread.

Ronni Marker26-Dec-09 2:32

Ronni Marker

26-Dec-09 2:32

Nope, not really. Well I could move to backgroundworker... But there should(right?) be a way to abort the thread without getting into the deep end.

Re: Aborting a Thread.

Luc Pattyn26-Dec-09 3:00

Luc Pattyn

26-Dec-09 3:00

As Nick and Albahari say, you should not even want to abort a thread, aborting it will leave a lot of objects in an unknown state, putting the app at the risk of a deadlock; how about things that may be locked and never will be unlocked again?

You really need the cooperative approach for thread control.
And a healthy way to access GUI Controls, hence the reference to my article.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

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