Re: Dispose pattern - C# Discussion Boards

Christian Graus4-Jun-07 20:51

Re: Pattern Matching in C# [modified]

4-Jun-07 20:51

You can use a maskedtextbox, or use regex, or use char.IsDigit, etc, in a key pressed event handler.

e.KeyCar LIKE "[0-9.]" is doing a regex pattern match, which is wasteful compared to char.IsDigit, but with different syntax, it works fine in C#.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )

KKrista4-Jun-07 21:34

KKrista

4-Jun-07 21:34

How about using RegularExpressionValidator control of C#?

-- modified at 4:25 Tuesday 5th June, 2007

Regards,
Murali

Christian Graus4-Jun-07 22:29

4-Jun-07 22:29

That does something entirely different, a regular expression validator tells you if your input was formatted correctly. He wants the control to not allow invalid input.

M. J. Jaya Chitra4-Jun-07 22:51

4-Jun-07 22:51

I have to allow only the nos so I tried by checking the keyvalue so it is checking fine but it should not be allowed to be in the textbox know but whenever i am setting e.keyvalue=0, it is giving that it is a read only property, so plz give me a hint how to disable the invalid characters and to allow only nos and .(dot).

Best Regards,
M. J. Jaya Chitra

Christian Graus4-Jun-07 23:00

4-Jun-07 23:00

if (!char.IsDigit(e.KeyChar) && e.KeyChar != '.')
{
e.Handled = true;
}

Something like that. setting handled to true stops the base class from handling the key press ( so it is then ignored )

Thank you

M. J. Jaya Chitra4-Jun-07 23:09

Dispose pattern [modified]

4-Jun-07 23:09

Thank you so much it is working well and good.
Once again Thank you

Best Regards,
M. J. Jaya Chitra

cateyes994-Jun-07 20:29

cateyes99

4-Jun-07 20:29

When we implement the dispose pattern, in protected virtual void Dispose(bool disposing), we need to say if disposing is true, then dispose managed resources as below:

protected virtual void Dispose(bool disposing)
{
  if (!this.disposed)
  {
    if (disposing)
    {
      // Dispose managed resources.
    }
    // Dispose unmanaged resources.
  }
  disposed = true;
}

When we make a call explicitly to this method with disposing = true, in public void Dispose() as below:

public void Dispose()
{
  Dispose(true);
  GC.SuppressFinalize(this);
}

the managed resources will be explicitly disposed. But why do we need to dispose managed resources explicitly in protected virtual void Dispose(bool disposing). Won't they be disposed automatically by the GC finally after the object reach the end of its life?

Secondly, since those are managed resources, how can we get our own hands on to release them? For example, if we allocate some chuncks of memory on heap (i.e, instantiate classes), is there a way for us to release them explicitly? (Setting the references to nothing doesn't mean that, it just tells .Net that we don't need them any more, they can be recollected from this point of time. And this is actually unnecessary. Right?)

Thanx a lot.

-- modified at 20:00 Tuesday 5th June, 2007

Re: Dispose pattern

Christian Graus4-Jun-07 20:52

sms.ud = work.msg.Content

4-Jun-07 20:52

Because you have no idea when the GC will be called, and the Dispose pattern is used to free unmanaged resources like bitmaps or database connections, so you can count on them becoming available right away.

Re: Dispose pattern

S. Senthil Kumar5-Jun-07 4:57

S. Senthil Kumar

5-Jun-07 4:57

cateyes_99 wrote:
Setting the references to nothing doesn't mean that, it just tells .Net that we don't need them any more, they can be recollected from this point of time.

But what about other managed objects that wrap unmanaged resources. Things like File, Pen etc.? For example :-

class TheDisposable : IDisposable
{
   IntPtr handle;    //Direct unmanaged resource
   FileStream stream;//Managed but wraps an unmanaged resource

   public void Dispose
   {
      Dispose(true);
      GC.SuppressFinalize(this);
   }

   protected virtual void Dispose(bool disposing)
   {
      if (disposing)
      {
         stream.Dispose();
      }
      CloseHandle(handle);
   }

   ~TheDisposable() { Dispose(false); }
}

If you don't explicitly dispose the stream here, you'd have to wait for the finalizer for that particular FileStream object to run (assuming it has a finalizer).

Like you said, there is no need (usually) to set references to null in Dispose, as the GC is intelligent enough to figure out that an object has no live references.

Regards
Senthil [MVP - Visual C#]
_____________________________
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Re: Dispose pattern

cateyes995-Jun-07 11:17

cateyes99

5-Jun-07 11:17

Thanks. It makes much clear

abdulsamad.shaik4-Jun-07 19:55

abdulsamad.shaik

4-Jun-07 19:55

hi..

in a class method like example : methodname(work obj) i pass the parameter of work object.
in that method i want to use the properties of message class like this

sms.ud = work.msg.Content

suggest me the best way so that i can proceed

Re: sms.ud = work.msg.Content

Christian Graus4-Jun-07 20:53

Re: sms.ud = work.msg.Content

4-Jun-07 20:53

What's the issue exactly ?

Muammar©4-Jun-07 20:58

Muammar©

4-Jun-07 20:58

English please Unsure | :~

Smile: A curve that can set a lot of things straight!
(\ /)
(O.o)
(><)

retreive the name of the image

dinosors4-Jun-07 19:50

dinosors

4-Jun-07 19:50

i've created thumnail of picture from a folder
i wanna know the name of the picture that i've clicked on
then i added an EventHandler to each pic but when i used a ImageLocation they don't return anything
so please help

public void pb_Click(object sender, EventArgs e)
{
if (pbSel != null)

pbSel.BorderStyle = BorderStyle.None;
PictureBox pb = (PictureBox)sender;
pb.BorderStyle = BorderStyle.FixedSingle;
pbSel = pb;
string test ="test";
com_image.Text = pb.ImageLocation+"test";

}

thanks

Re: retreive the name of the image

Christian Graus4-Jun-07 20:53

Re: retreive the name of the image

4-Jun-07 20:53

An image does not store it's path internally.

Luc Pattyn5-Jun-07 0:55

Luc Pattyn

5-Jun-07 0:55

Hi,

PictureBox.ImageLocation will be set automatically only by PictureBox.Load(URL).

When you load the image and calculate the thumbnail you could store the filename
yourself in PictureBox.ImageLocation; then you can retrieve it afterwards...

Smile | :)

Luc Pattyn

[My Articles] [Forum Guidelines]

Panel Manip (Simple but a great head ache)

M. J. Jaya Chitra4-Jun-07 19:15

Re: Panel Manip (Simple but a great head ache)

4-Jun-07 19:15

I am having 4 panels in my windows form. In that at a time only one panel has to visible and others has to be hidden. I tried it by setting the visibility as true for one panel and false to others but while debugging the visibility is not setting to true and i tried by callinf bringtofront method that time also what i have set in the design time is coming but others are not coming to the front WHY?

Can anyone answer me plz?

note: in the design time all my panels visibility is set to true

Best Regards,
M. J. Jaya Chitra

Christian Graus4-Jun-07 20:54

4-Jun-07 20:54

M. J. Jaya Chitra wrote:
I tried it by setting the visibility as true for one panel and false to others but while debugging the visibility is not setting to true

Well, that just plain can't be. Unless some of your panels are sitting inside some of the others ? Then disabling an outer panel will disable the inner one.

Thank you

M. J. Jaya Chitra4-Jun-07 22:46

4-Jun-07 22:46

Thank you so much

Best Regards,
M. J. Jaya Chitra

VC++ to C#

Kabirdas Jaunjare4-Jun-07 17:45

Kabirdas Jaunjare

4-Jun-07 17:45

i want to develop window in VC++ as a COM component and thene . use this component in .NET environment in C# client to put..control over that window..
how to do that..i wanna know..? D'Oh! | :doh:

sam

Re: VC++ to C#

Christian Graus4-Jun-07 20:55