Re: When to choose Static Method/Variables rather than Instance Method/Variable - C# Discussion Boards

Re: Building unused methods in a class

Dave Kreskowiak19-Sep-06 11:50

Dave Kreskowiak

19-Sep-06 11:50

bashiwala wrote:
I am adding a whole System.Web assembly, will that greatly increase the size of the application or not

No, it won't. Any referenced code is not compiled into your app.

bashiwala wrote:
Later I realized that either I will have to port the System.Web assembly with my application or the User of my application must have System.Web in his PC

You don't have to install it with your app. It's already part of the .NET Framework, which everyone who uses your app has to have installed before they can launch your .EXE.

bashiwala wrote:
Now, How can I decide if I should choose "Copy to Output Directory" of a referenced assembly

If it's part of the .NET Framework, then you don't have to copy anything. If it's a custom written assembly, something you've put together, then you can select "Copy to Output Directory".

bashiwala wrote:
Should I assume that all System.* namespaces are available in All Windows user's pc so that I dont need to port any System.* assembly

If it's in .NET Framework, then you can safely assume it's installed on the users PC. These[^] are all the classes that come in the .NET Framework that the users have to install.

Dave Kreskowiak
Microsoft MVP - Visual Basic

Re: Building unused methods in a class

Nadia Monalisa19-Sep-06 14:53

Nadia Monalisa

19-Sep-06 14:53

Hi Dave,
Thanks a lot for your detailed reply. Now I have understood. Smile | :)

When to choose Static Method/Variables rather than Instance Method/Variable

Nadia Monalisa19-Sep-06 8:55

Nadia Monalisa

19-Sep-06 8:55

Hello,
It is my experience that, using Static Method makes life very easy. When I need a method call, I just simply call ClassName.MethodName().

But what is the key point I must be careful about using Static Method or Static Variable rather than Instance Method or Instance variable ?

Is Static method a problem for multi threaded application ? if so, then how come most of the System class has static method like, File.Exists(), File.ReadAllText(....), etc.. ?

Regards...

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Dave Kreskowiak19-Sep-06 10:03

Dave Kreskowiak

19-Sep-06 10:03

They have nothing to do with threading at all. It comes down to data encapsulation.

If you look at the FileInfo and File classes in the System.Io namespace, you'll see that they do the exact same things, only in slightly different ways. FileInfo is an instance implementation and File is static.

You can copy a file either of two ways. You can create an instance of a FileInfo object, then call the .CopyTo() method on it, passing in just the destination file name since the object already knows that it is the source path.

FileInfo myFile = new FileInfo("C:\\Test.txt");
myFile.CopyTo("D:\\TEST\\Test.txt");

Or you can use the static methods exposed by the File class, where you have to specify both the source and the destination paths:

File.Copy("C:\\Test.txt", "D:\\TEST\\Test.txt");

The FileInfo class encapsulates a single file where you can get properties on that file and tell it to delete, copy, or move itself. All of the methods will only work on that instance of the class.

The File class doesn't encapsulate anything. It requires you to specify which file it's going to work on with every single call you make.

You can read more about it here[^]. 'Cause if most of what you're writing is static methods, you're completely missing the point of object-oriented programming.

Dave Kreskowiak
Microsoft MVP - Visual Basic

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Guffa19-Sep-06 10:35

Guffa

19-Sep-06 10:35

If the method doesn't use any data from the instance of the class, it should be static. For example, the method File.Exists doesn't use any data other than the string that you send as a parameter.

Static methods are not a problem for multi-threaded applications.

A static variable is stored in the class rather than the instance of the class, so there is always one of the variable no matter if there are zero or a million instances of the class.

As all threads share the same variable, you have to use locking to make the use of a static variable thread safe.

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Re: When to choose Static Method/Variables rather than Instance Method/Variable

Nadia Monalisa19-Sep-06 10:48

Nadia Monalisa

19-Sep-06 10:48

Hi Guffa,
Thanks for your suggession. It is a bad news for me that you said I must use Locking of static variabls to make it thread safe. Now I will have to convert all my static variables to instance variables in my whole application as those variables are shared by threads. Cry | :((

((((((

If I use instance variable, then I dont need to lock as long as the instance is created within the thread, right ?

Is this locking required for only static variables ? or do I need to lock Static Methods too ?

I did not like to learn Lock chapter of C#. Is there any simple snippet you can show me to lock a variable ?

Thanks and regards
Emran.

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Christian Graus19-Sep-06 13:19

Christian Graus

19-Sep-06 13:19

Making the variables not static will not solve your problem. If your app is multi threaded, and the threads all access a variable that exists in a single instance, then you need to use locking. Static simply defines the fact that there is only one variable, but if you move the variable to an instance, and pass an instance between threads to access the variable, you've created a new problem ( passing a reference to the class ) and not solved the old one ( multi threads all hitting the same variable ).

bashiwala wrote:
I did not like to learn Lock chapter of C

Why not ?

bashiwala wrote:
Is there any simple snippet you can show me to lock a variable ?

Isn't it just the lock keyword and a block that does the work ?

bashiwala wrote:
Is this locking required for only static variables ? or do I need to lock Static Methods too

Any code which changes a variable where that instance is shared across threads needs to be locked. Do you understand what the issue is ?

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Nadia Monalisa19-Sep-06 14:38

Nadia Monalisa

19-Sep-06 14:38

Hi Christian,
Thanks a lot for detailed answer.

Ok, I tried to learn the lock but I did not understand from MSDN documentation.

Say for example, I have following variable, and method,

..............................................................

static int a = 8;

public static void myMethod(string myValue)
{
// do some change on XML.
}

..............................................................

Now, How can I just lock both of this variable and method ?

Will the following snuippet work ?

..........................................................
lock
{
static int a = 8;
}

lock
{
public static void myMethod(string myValue)
{
// do some change on XML.
}

}
................................................................

thanks and regards
Emran

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Christian Graus19-Sep-06 14:47

Christian Graus

19-Sep-06 14:47

No, you've got it wrong:

public static void myMethod(string myValue)
{
lock
{
// do some change on XML.
}
}

You're locking the portion of code that needs to be atomic ( it needs to all run before another thread tries to run any of it ).

You want to lock as much as you need, and as little as possible.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Nadia Monalisa19-Sep-06 16:25

Nadia Monalisa

19-Sep-06 16:25

Hi Christian,
Thank a loot for the help.

I have some const variables in my form like,

public const string dataPassword = "abcd";

public static string myValue = "1234";

This variable is shared by all threads simultaneously but this value is not changed by any of the thread. So, do you think I must use lock to protect this kind of variables ?

Thanks and regards
Emran

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Christian Graus19-Sep-06 16:40

Christian Graus

19-Sep-06 16:40

I'm not sure that you're getting the concept. The concept is, if two threads change a value, it's possible that data will be lost if one is half way through doing something and the other one steps in. If values are not being changed, no locking is required.

you would, however, be better off doing something like this:

public static string DataPassword { get { return "abcd"; } }

or at least mark then all readonly. static values can still be changed.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Nadia Monalisa19-Sep-06 17:30

Nadia Monalisa

19-Sep-06 17:30

Hi Christian,
thanks a lot.
Now I understood the concept. Smile | :)

Re: When to choose Static Method/Variables rather than Instance Method/Variable

Nadia Monalisa2-Oct-06 4:32

Nadia Monalisa

2-Oct-06 4:32

Hi,
I am grateful for your previous guidances.

Would you please help me about a confusion.

In my Application, I have an XML file where only one thread WRITEs to this file. But multiple thread shares this file for READING. Do I need to apply LOCK in this case? Is there any chance of thread conflict while one thread is trying to write to the file and another thread is trying to read the file? (I thought confliction arises only when both of the threads are trying to write to the file).

Regards,
Emran

Left Function in C#

MyRunner2319-Sep-06 7:34

MyRunner23

19-Sep-06 7:34

Hi All,

anyone know the left function in C#?

Thanks

Re: Left Function in C#

Jon Sagara19-Sep-06 7:41

Jon Sagara

19-Sep-06 7:41

String.Substring(start, length)[^]

Jon Sagara
When I grow up, I'm changing my name to Joe Kickass!
My Site | My Blog | My Articles

Re: Left Function in C#

Eric Dahlvang19-Sep-06 7:45

Eric Dahlvang

19-Sep-06 7:45

String cMyString = "This is my string";
MessageBox.Show(cMyString.<code>Substring(0,5)</code>);

[edit]oops...Jon got here first...[/edit]

--EricDV Sig---------
Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them.
- Laurence J. Peters

Re: Left Function in C#

samtam19-Sep-06 22:13

samtam

19-Sep-06 22:13

Fellows i didnt get it. why is it called "Left", further clarify me

thanks in advance

Re: Left Function in C#

Eric Dahlvang20-Sep-06 4:33

Eric Dahlvang

20-Sep-06 4:33

There is no "LEFT" function, but you can use Substring to return the left portion of a string:

The following will display: This

String cMyString = "This is my string";
MessageBox.Show(cMyString.Substring(0, 4));

The following will display: This is

MessageBox.Show(cMyString.Substring(0, 7));

--EricDV Sig---------
Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them.
- Laurence J. Peters

Re: Left Function in C#

samtam20-Sep-06 20:26

samtam

20-Sep-06 20:26

Thanks alot
i was only confused coz of the term 'LEFT', otherwise i know how to use this method.

How to capture the URL?

zhoujun19-Sep-06 5:11

zhoujun

19-Sep-06 5:11

I mean when I browse webpage in IE browser.There are many URL links on page, when mouse move through webpage,how can i capture the URL address that mouse currently point to?I mean capture the address from my own program!

Hope you catch my meaning.Thanks

My Blog:August 12,2006,Rhythm of The Rain.

Calculating scientific notation?

Goalie3519-Sep-06 5:10

Goalie35

19-Sep-06 5:10

How can I add scientific values such as "2 to the 3rd power" plus "2 to the 4th power"?

Thanks

-Goalie35

Re: Calculating scientific notation?

Stefan Troschuetz19-Sep-06 5:24

Stefan Troschuetz

19-Sep-06 5:24

Math.Pow(2, 3) + Math.Pow(2, 4)

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning." - Rick Cook

www.troschuetz.de

Set resolution in Metafiles

cubeccu19-Sep-06 5:07

cubeccu

19-Sep-06 5:07

Hi all,
I wonder if I can find how to set the resolution for a Metafile.
I create Graphics object using

IntPtr hwnd = (IntPtr)Win32.GetDesktopWindow();
return Graphics.FromHwnd(hwnd);

The resolution il always 96x96. Since I need to print the Metafiles, I wish to have at least 600x600.
I tried also to create graphics from a bitmap with resolution 600x600 but it doen't work.

Any suggestion?

writing to string resource

likefood19-Sep-06 4:57

likefood

19-Sep-06 4:57

Ok, I know this sounds noob, but I'm learning as I go...
Up to now, I have read in various strings (for prog settings) from a separate text file. I'd like to put all that string info in the program.

I have embedded four [name]=[value] lines into the program (using resgen, going from .txt to .resx to .resources, and using the /resource csc.exe switch), but the ResourceManager only lets me read the information. If I only needed to read the info, I'd just use private string members in the program itself. However, the values change at runtime, and I'd like to save the changes (without using other files outside of the executing file).

I've looked briefly (I try to search first, before running to the forum for help), but didn't see anything that would help me just save this information.

-Daniel
Typing too fast fro my owngood

Problems with a custom tooltip [modified]

Gags66619-Sep-06 4:36

Gags666

19-Sep-06 4:36

Hi there!

I've made some kind of tooltip for items included in a ListBox which appears near the cursor when the it's hovering an item in the ListBox.
Because I didn't knew better how to make a tooltip I did it with a simple Windows-Form with some options to make it look like a nice tooltip. When an item in the listbox is hovered by the mouse the tooltip shows up as I want it to. But I still have a few problems:

1. The tooltip-window is always getting the focus and that makes the main-form flickering. How can I prevent this? I set the focus back manually but it's still flickering a bit. Best thing would be the focus wouldn't change at all or something like that.

2. Setting the location for the tooltip makes it act weird. When I set it in the constructor or after the initialization of the tooltip (with this.Top and this.Left as well es with this.Location both based on Cursor.Position) it always appears at the same starting location. By moving the mouse and triggering the event it's moving along across the screen but always on the same route ignoring the cursor-position (seems like the position is stacking its values somehow). When I set it after displaying the form (with Show()) it works.

3. Is this actually the right way to create a tooltip or something like a flying info-box? (I mean by using a Windows-Form and opening it on demand.) It doesn't seem so for me because of the problems I have it looks like it's not ment to be done this way.

I hope someone can help me. Frown | :(

Maybe you want to see the code of my MouseMove-Event:

int taskIndex = listBoxTasks.IndexFromPoint(e.Location);

if (taskIndex > -1) // Check if there's an item under the cursor.
{
    Task currentTask = ((Task)bindingSourceTasks[taskIndex]); // Get the current item.

    if (currentTask != lastTask) // Check if it's not the same like before.
    {
        if (tooltip != null) // Check if tooltip is already open.
        {
            tooltip.Close();
        }

        tooltip = new frmTooltipComponent(currentTask); // Open new tooltip.
        tooltip.Show(); // Show tooltip;
        this.Focus(); // Set focus back to main window.
        tooltip.Top = Cursor.Position.Y; // Set tooltip Y-position.
        tooltip.Left = Cursor.Position.X + 50; // Set tooltip X-position.
        lastTask = currentTask;  // Remember current item.
    }
    else // If same item like before just set new tooltip position.
    {
        tooltip.Top = Cursor.Position.Y; // Set tooltip X-position.
        tooltip.Left = Cursor.Position.X + 50; // Remember current item.
    }
}
else if (tooltip != null) // If no hovered item check if tooltip is open.
{
    tooltip.Close(); // Close tooltip.
    lastTask = null; // Clear last remembered item.
}

In MouseOut-Event of the ListBox I'm also closing the tooltip and clearing the last remembered item.

-- modified at 11:15 Tuesday 19th September, 2006

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