C# Discussion Boards - CodeProject

xkrja30-Mar-10 20:23

30-Mar-10 20:23

A couple of days ago I asked here how to ensure that a generic list isn't modified while an operation like Find() or Exist() is performed on the list. I was recommended to use the lock-statement.

Now I would like to know if it's enough to lock the list while adding or removing items from it? Or do I need to lock it while performing a non-changing operation like Find() on the list as well?

Thanks for help!

Re: Synchnroization with lock statement

SeMartens30-Mar-10 21:26

SeMartens

30-Mar-10 21:26

Hi,

you have to use the lock-statement while adding and removing and also for non-changing operations.

The lock-statement is like a monitor (imagine a gatekeeper) that allows execution of a critical code block. So to be sure if you have several critical blocks that only one block is executed at one time you have to use the same gatekeeper for all blocks.

Example:

<br />
// declare a lock-object (the gatekeeper)<br />
private Object thisLock = new Object();<br />
<br />
public void AddItem(object item) {<br />
  lock(thisLock) {<br />
     // add to the list<br />
  }<br />
}<br />
<br />
public object FindItem(object criteria) {<br />
  lock(thisLock) {<br />
     // search within the list<br />
  }<br />
}<br />

Be pay attention that all access to the list is within a lock-statement using the same object (gatekeeper).

Hope this helps a bit.

Regards
Sebastian

It's not a bug, it's a feature!

Check out my CodeProject article Permission-by-aspect.

Me in Softwareland.

Re: Synchnroization with lock statement

xkrja30-Mar-10 22:10

xkrja

30-Mar-10 22:10

Thanks for the reply!

You're right. I did a test and tried it out. But is there some way around this? So while a non-changing operation is performed on the list other non-changing operations can get access to the list as well? So that only modifications to the list can be stopped while theese non-changing operations is happening to the list?

The reason is I'm creating a WCF service and each client contacts the service on a different thread. Each time a clients calls a method on the service the list is searched. This means if several hundreds of clients are connected every thread is locking the list and it takes some time to search there will be a real performance decrease.

A solution I guess is to wrap all non-changing operations in try-catch blocks and skip the lock but that seems like a real hack!

EDIT: It's a static list we're talking about in this case.

Thanks again!

Re: Synchnroization with lock statement

SeMartens30-Mar-10 22:21

SeMartens

30-Mar-10 22:21

Yup, this solution is a real hack. But the problem you refer to is the reader/writer problem. And guess what, the framework contains a solution for this called the ReaderWriterLock:

http://msdn.microsoft.com/en-us/library/system.threading.readerwriterlock.aspx[^]

Didn't used it myself but it seems easy to utilize.

It doesn't matter if it is a static list as long as you are using static methods to access the list (using a static monitor).

EDIT: I have to correct myself: You don't need static methods. All you have to do is using a static monitor (gatekeeper).

Regards
Sebastian

It's not a bug, it's a feature!

Check out my CodeProject article Permission-by-aspect.

Me in Softwareland.

Re: Synchnroization with lock statement

xkrja30-Mar-10 22:26

xkrja

30-Mar-10 22:26

I found it just before I saw your answer Smile | :)

It seems there are two solutions: ReaderWriterLock and ReaderWriterLockSlim.

It seems to exactly what I need!

Thanks for your help!

ProgresBar

Anil Kumar.Arvapalli30-Mar-10 20:20

Anil Kumar.Arvapalli

30-Mar-10 20:20

Iam Using 2 Threads in My Application. 2 Threads has to Update the single Progress Bar, so that user will come to know when the Process is completed. iam very nave to C# can some body help me out regarding this Please.... Thanks in Advacne.....

Or else Please suggest some Sample....

Re: ProgresBar

Khaniya30-Mar-10 20:24

Khaniya

30-Mar-10 20:24

You can use this for update UI(progressbar) in thread

http://www.codeproject.com/tips/67548/Changing-a-WinForms-Control-on-the-UI-Thread-from-.aspx[^]

and for synchronization you can use lock block in your application

Smile | :)

Thanks

Life's Like a mirror. Smile at it & it smiles back at you.- P Pilgrim
So Smile Please

Play sound

jojoba201130-Mar-10 20:06

jojoba2011

30-Mar-10 20:06

I am writing a reminder software and now i want to play mp3 file when alerting the reminder to the user !

I have done something for wav file to play in background without opening an software.

Now my Question is that how to play Mp3 file form Alert without opening any software like windows Media Player!

Re: Play sound

Khaniya30-Mar-10 20:18

Khaniya

30-Mar-10 20:18

you can convert your wav file into executable. some free software available on net

http://www.f2ko.de/English/a2e/download.php[^]

thank you

Smile | :)

Life's Like a mirror. Smile at it & it smiles back at you.- P Pilgrim
So Smile Please

Re: Play sound [modified]

jojoba201130-Mar-10 21:10

jojoba2011

30-Mar-10 21:10

your solution is diffrent from my Question!

modified on Wednesday, March 31, 2010 3:45 AM

Re: Play sound

Kristian Sixhøj31-Mar-10 0:14

Kristian Sixhøj

31-Mar-10 0:14

How big/long is the mp3 file?

If it isn't too big, I'd suggest converting it to a wave file, then using the SoundPlayer class[^] to play it.

Note that the filesize will increase when converting from mp3 to wav.

If you insist on keeping the file as an mp3, have a look at this article:
MP3 Player for Windows 7[^]

Kristian Sixhoej
"Invisible women out to kill ya - Oh, great!"

Xml Deserialization

VCsamir30-Mar-10 19:43

VCsamir

30-Mar-10 19:43

hi friends,

i am using xmlclass serailization to read the Xml File

///<Order xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" orderId="1" version="3.1.0" xmlns="http://www.abc.com/schemas/imaging/rps/order/2007/01/" ///>

</order>

XmlTextReader reader = new XmlTextReader(filename);

try

{

XmlSerializer serializer = new XmlSerializer(typeof(Class_name));

Class_object = (Class_name)serializer.Deserialize(reader);

reader.Close();

}

catch (Exception e)

{

reader.Close();

return;

}

it says that "{<Order xmlns='http://www.abc.com/schemas/imaging/rps/order/2007/01/>' was not expected."}"

my class defination is as follows

[XmlRoot("Order")]

public class Class_name

{

[XmlAttribute]

public string orderId;

[XmlAttribute]

public string version;

//default constructor

}

}

Can Anyone help me to resolve this!!

Re: Xml Deserialization

Arun Jacob30-Mar-10 20:09

Arun Jacob

30-Mar-10 20:09

VCsamir wrote:
Order

VCsamir wrote:
order

Opening and closing tags are not matching. XML tags are case sensitive.

Arun Jacob
http://codepronet.blogspot.com/

Re: Xml Deserialization

VCsamir30-Mar-10 21:37

VCsamir

30-Mar-10 21:37

hi ,

Opps sorry friends..
The opening and closing tags are matching i have put "//" only because to show the example..(when i was posting the same code the <> tags were getting invisible D'Oh! | :doh:

)i have tried opening the xml in iexplorer it opens fine..

Thanks ..

Regards
Samir

Re: Xml Deserialization

Mirko198030-Mar-10 21:43

Mirko1980

30-Mar-10 21:43

You are not specifying the namespace in the XmlRoot attribute

Re: Xml Deserialization

VCsamir4-Apr-10 20:21

VCsamir

4-Apr-10 20:21

Thanks Sir !!

I problem is solved.. i set the the namespace atrribute in the root!! thanks once again for being so kind..

Regrds
Samir

Passing Value From One Form To Another! [modified]

Sr...Frank30-Mar-10 18:22

Sr...Frank

30-Mar-10 18:22

Hi,
I am trying to pass value from one windows form to another in desktop application using C#.
I have created two text boxes on Form1 and a button, on button click I am creating Form2 and From2 contains one button, on this button click I have to pass value from Form2 to Form1 textboxes.

I have created Properties in Form1.

public string Emp
{
get
{
return strEmp;
}
set
{
strEmp = value;
}
}

public string EmpID
{
get
{
return strEmpID;
}
set
{
strEmpID = value;
}
}

And on Form1 button click:

private void button1_Click(object sender, EventArgs e)
{
Form2 fr = new Form2();

this.textBox1.Text = strEmp ;
this.textBox2.Text = strEmpID ;
fr.ShowDialog();
}

On Form2:

private void button1_Click(object sender, EventArgs e)
{
Form1 fr = new Form1();
fr. Emp = "Alex";
fr. EmpID = "1121";
this.Close();
}

This code is not working, Please let me know where I am wrong.

Thanks,

modified on Wednesday, March 31, 2010 12:54 AM

Re: Passing Value From One Form To Another!

Anubhava Dimri30-Mar-10 18:27

Anubhava Dimri

30-Mar-10 18:27

Read this article

Passing Values between Forms in .NET 1.x with C# and VB.NET examples[^]

If you can think then I Can.

Re: Passing Value From One Form To Another!

Praveen Raghuvanshi30-Mar-10 18:45

Praveen Raghuvanshi

30-Mar-10 18:45

First there is a compilation error at the 2 statements in which you are assigning variables to the textbox as name of the variables differ.

Second, you are setting the values in the text box of first form after calling the showdialog. So, the values can e displayed only after you close the dialog box.

Third, You are creating a new instance of form1 on the click of button on form2. It won't set the values on the initial form.

Praveen Raghuvanshi
Software Engineer,

India.

Re: Passing Value From One Form To Another!

Sr...Frank30-Mar-10 18:56

Sr...Frank

30-Mar-10 18:56

Thanks for your time but please let me know the right solution.

Re: Passing Value From One Form To Another!

Praveen Raghuvanshi30-Mar-10 21:43

Praveen Raghuvanshi

30-Mar-10 21:43

The link provided by 'eg_Anubhava' explains the communication in a clear way.

Praveen Raghuvanshi
Software Engineer,

India.

Re: Passing Value From One Form To Another!

DaveyM6931-Mar-10 0:43

DaveyM69

31-Mar-10 0:43

In addition to the article already linked - here's[^] a quick Tip that shows how to do it concisely

Dave

If this helped, please vote & accept answer!

Binging is like googling, it just feels dirtier. (Pete O'Hanlon)

BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

Repositioning the cursor

skhan1730-Mar-10 12:49

skhan17

30-Mar-10 12:49

Hello,
I am looking for ways to reposition the cursor when I am clicked on the first menu item from a form menu. It should create a jumping effect so the user doesn't have to scroll through the other menus which don't have a child menu.

for example.... one file menu has 4 items. Namely 1, 2, 3, 4 now only item 2 has child menu items. namely 2.1, 2.2, 2.3. I want the cursor to be on 2.1 when the user brings the mouse on 2.

Please let me know how to do that. I am trying the following:

private void toolStripMenuItem2_MouseHover(object sender, EventArgs e)
        {
            toolStripMenuItem2.ShowDropDown();
            Point LocalMousePosition_1 = this.PointToClient(Cursor.Position);
            System.Windows.Forms.Cursor.Position = new Point(500, 500);  //This just repositions the cursor to 500,500 position but not in the net child menu. This is where I am stuck.

            //Point LocalMousePosition_2 = toolStripMenuItem2_1.PointToClient(Cursor.Position);
            MessageBox.Show(LocalMousePosition_1+"Happy New Year to DOTNETSPIDER.COM guys");        
        }

Re: Repositioning the cursor

PIEBALDconsult30-Mar-10 12:56

PIEBALDconsult

30-Mar-10 12:56

That sounds user-hostile -- I wouldn't use your application if it did that.

Re: Repositioning the cursor

skhan1730-Mar-10 13:11

skhan17

30-Mar-10 13:11

It doesn't matter if it's hostile or not, I need it now for some reason... let's just say all the supervisors in the MSc. program are crazy...... if you know a solution please help me ...otherwise please mind your own business....

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