Re: static variable - C# Discussion Boards

Dave Kreskowiak30-Sep-04 6:01

30-Sep-04 6:01

Your question would be better handled in the ASP.NET Forum. This is a web development/ASP.NET question, regardless of the language that the code-behind is written in.

The static variable idea won't work considering that ASP.NET, as any HTML page, is stateless. You have to save the values to hidden fields on the page, to be read back when the page is posted back to the server, or in the Session object, or somewhere else that can handle state. And, no, it won't become global. There is no such thing in the .NET Framework.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

goatstudio30-Sep-04 6:22

goatstudio

30-Sep-04 6:22

Dave Kreskowiak,

Thanks for the info. Smile | :)

My static variable actually work on the page... just that I am worry it become global. Your answer make me feel better. Big Grin | :-D

p/s: I post it here coz I am using C# in my asp.net. Anyway thanks for reminding me. Poke tongue | ;-P

Heath Stewart30-Sep-04 6:22

30-Sep-04 6:22

While I normally agree with Dave, I don't see this as specific to ASP.NET so I'll bite.

This won't even compile. You cannot declare fields (a static int Counter looks like a field to the compiler) inside method implementations.

If you need to declare a static variable, do so in the class (your derivative page) like so:

static int Counter = 0; // private
 
// Override OnEventName when possible - it's faster with more control
protected override void OnLoad(EventArgs e)
{
  Counter++;
  base.OnLoad();
}

This will increment for the lifetime of the object, which is alive for as long as the AppDomain is alive in which it was created. For Windows Forms applications, this is typically as long as your application is running (your application could, however, create a new AppDomain). With ASP.NET, this is for as long as the web application doesn't need restarting (like after editing the Web.config file for the site or application; or, again, unless you created a separate AppDomain for some reason).

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Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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goatstudio30-Sep-04 6:27

goatstudio

30-Sep-04 6:27

Heath Stewart,

Thanks for the explaination! Big Grin | :-D

You are right, I actually declare the static variable outside the Page_Load method. My mistake here... Poke tongue | ;-P

I just want to make sure that, as long as the static variable won't share by other sessions in the same server... it will be fine... Wink | ;)

Thanks guy... Wink | ;)

Heath Stewart30-Sep-04 6:42

30-Sep-04 6:42

Statics are always within the context of an AppDomain, so if your process consists of two or more AppDomains statics will be different.

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Developer Division Sustained Engineering
Microsoft

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Dave Kreskowiak30-Sep-04 8:33

30-Sep-04 8:33

Hey Heath!

How's life in the shadow of an actively rumbling volcano? Wink | ;)

I thought he was asking if it was possible to persist a session-specific value using a static, like you've suggested. I did't think that's possible, but I could be wrong? Is the AppDomain session-scoped or application-scoped? Seems like a dumb question, I know. But just for clarification purposes...

Also, just to point out for future readers ... yeah, right! Wink | ;)

... using a Static such as this, in either Session or Application scope, does not propogate it's value acrossed multiple servers hosting the same web application. So, if you have two or more web servers running the same application, say for load balancing purposes, all servers will have different values for the Static "global" variable.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Heath Stewart30-Sep-04 9:10

30-Sep-04 9:10

Dave Kreskowiak wrote:
How's life in the shadow of an actively rumbling volcano?

Exciting! I've been through tornados having been from the midwest, but this is a new experience. I had a lot of interest in volcanoes (and earthquakes) when I was younger (did a fair share more than just "class projects" on them) so this will be fun to see in person. If I get a chance I'll be taking some pics. Smile | :)

It's not expected to be dangerous to the greater Puget Sound area, though, so I'm not worried.

What is exciting is that I've killed two potentially deadly spiders in our new apartment, all within a week of moving in! While they look like brown recluse spiders, 1) those are only supposed to be in the south-east, and 2) they're often mistaken for hobo spiders, which are in this area (and just as potentially deadly).

Back to the topic at hand...

As far as the problem goes, it really all comes down to AppDomains. A process can have more than one AppDomain, and a web application is an AppDomain. As long as the AppDomain is active, the statics are, well, static. Since an AppDomain cannot span multiple machines, what you said about services is true.

To the original poster, if you want a "global" variable across multiple server or applications, you either need to persist it in some storage medium (like a database, although that can be pretty slow depending on load) or use .NET Remoting which allows communication between multiple AppDomains (through indepedent transport and formatting channels). You could, for example, have a singleton running on some machine and the separate servers communicate with the remoting object through a proxy (which you implement a mutex to lock the increment and/or decrement).

There's lots of different ways to solving the problem.

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Software Design Engineer
Developer Division Sustained Engineering
Microsoft

[My Articles]

Dave Kreskowiak30-Sep-04 10:57

30-Sep-04 10:57

Heath Stewart wrote:
Exciting! I've been through tornados having been from the midwest, but this is a new experience. I had a lot of interest in volcanoes (and earthquakes) when I was younger (did a fair share more than just "class projects" on them) so this will be fun to see in person. If I get a chance I'll be taking some pics.

Awsome! Big Grin | :-D

I'm so jealous! I've had that same, call it morbid, curiosity about how these things work and still have it to this day.

I've been within 500 feet of a tornado before, BUT COULDN'T SEE IT! because it was heavily rain-wrapped. All we saw, looking through the 8 foot tall plate glass windows in the front of the store Poke tongue | ;-P

, were roofs being torn off buildings ... what a let-down that was.

I've even had the pleasure of watching empty Coke cans slide back and forth acrossed my desk during earthquakes in and around South-East Michigan. I know, it's not an earthquake mecca and they're weak by Pacific Coast standards, but it's still pretty funny to try and balance on one foot while putting jeans on during an earthquake (1986 - epicenter in middle of Lake Erie).

If Mt St Helens blows again, we want pictures! LOTS of pictures! Setup a webcam if you have to! Who knows if the one at the Johnston Ridge Observatory[^] will be working if/when it does decide to erupt.

and now, back to our show...
--------8<--------------------------
I agree with your assessment of the speed of persisting Session info to an SQL server. It's as flexible a solution as your going to get, but it does tend to be a little slow. I've installed the SQL state server package that comes with, I can't remember which or where, but I think, ASP.NET or Visual Studio .NET Enterprise.

I've thought about both single and multiple server session state caching schemes. A single server solution is easy to implement, but has the downfall of not being scalable to support say, 15 IIS servers.

Mostly, I've wondered what the benefits, limitations and pitfalls are of a solution consisting of small cluster of servers, no more than 3 to start, each running a "Singleton" component, but sync'ing up their data on a real-time basis. These servers could possibly run behind a single-IP solution to facilitate fault-tolerance.

The list of ponderings I've come up with is pretty long... What would be the database synchronization requirements? What would the specification of the synchronation protocol look like? What kind of traffic load would just the synchronization protocol generate? There would probably have to be some kind of mechanism to ensure the consistancy of the state data before the next request comes in on the same session. What would happen if two requests came in on the same session, but the state servers were not able to sync up their data before the second request came in? How would the servers defend themselves against running out of memory since there would be no media to drop the database on? What would the memory requirements be? How would the servers detect a failed server? How would the synchronization protocol handle this situation? How would it handle the reintroduction of a restarted server? ... The list goes on and on...

What if we cahnged the scheme so that each server only holds a portion of the overall database instead of a full copy of it? Start a new list of ponderings...

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Transparent Panel

MarkMokris30-Sep-04 5:28

MarkMokris

30-Sep-04 5:28

I am using a DataGrid for display purposes only and would like to deactivate much of the default functionality as far as the user clicking on it. I have tried overridding OnMouseDown, but when the user clicks on a cell it still gets selected and goes into input mode. I need to disable this kind of behavior, but I still want to capture mouse events so I cannot really set Enabled = false.

My thought was to cover the client area of the DataGrid with a Panel. However, the Panel would need to be transparent, and I don't know how to do this. Is is possible? Is there a better solution?

Thanks!

Mark Mokris

Re: Transparent Panel

Heath Stewart30-Sep-04 6:32

30-Sep-04 6:32

Why not bind your DataGrid to a DataView that disables what you don't need? You can do so like this:

DataView view = new DataView(dataSet1.Tables["MyTable"]);
view.AllowDelete = false;
view.AllowEdit = false;
view.AllowNew = false;
dataGrid1.DataSource = view;

Using a DataView makes it easier to manage sorting and filtering, although you can still do that when binding to a DataSet or DataTable using the DataSet.DefaultViewManager.

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Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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Re: Transparent Panel

MarkMokris30-Sep-04 6:36

MarkMokris

30-Sep-04 6:36

Hi Heath,

Thanks for the response. I had already tried what your saying, but still when the user clicks on a cell, it gets selected and a text cursor appears. You will not be able to type anything, but I'd like to avoid the text cursor appearing.

Does anyone know, is it possible to create a transparent panel?

Thanks,

Mark

Re: Transparent Panel

Heath Stewart30-Sep-04 6:50

30-Sep-04 6:50

Yes, I do, but that's not the right way to do it and will only be supported on Windows 2000 and newer (for Windows NT platforms). This uses the SetLayeredWindowAttributes native API that you must P/Invoke, something we've discussed in this forum before and which a few articles on this site discuss.

However, there's still better ways. If you just don't want the DataGrid to respond to any user input (at least on cells, which begs the question of why you're even using the DataGrid then when either using a ListView or just drawing the items yourself would be sufficient), then use the DataGrid.HitTest in conjunection with overriding OnMouseDown to make sure that when a user is over a cell you don't call base.OnMouseDown to continue processing the notification message (WM_LBUTTONDOWN). This allows you to maintain the normal mouse message processing for other parts of the DataGrid while maintaining functionality for all supported platforms on which the CLI is implemented.

This posting is provided "AS IS" with no warranties, and confers no rights.

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

[My Articles]

word formatting bar

RomanD30-Sep-04 5:15

RomanD

30-Sep-04 5:15

Is there a control I can add to the textbox that is like the "formatting bar" in Word. I need the user to be able to choose font, color, etc... The question is, do I have to make that panel/bar from scratch or can I import it as a control from anywhere?

Re: word formatting bar

Dave Kreskowiak30-Sep-04 5:57

30-Sep-04 5:57

You'll have to either write your own Toolbar code to handle what all the buttons are supposed to do or you can use a commercially available control to handle the Toolbar, still writing the code that does what the buttons say they do.

A Textbox has very few properties that make it useful for editing and formatting like this. Why not use a RichTextBox control instead?

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Re: word formatting bar

RomanD30-Sep-04 6:09

RomanD

30-Sep-04 6:09

What I meant by textbox is RichTextBox, sorry. But is there a control for that or will I still have to write my own?

Re: word formatting bar

Dave Kreskowiak30-Sep-04 7:21

User clicks on dataGrid....

30-Sep-04 7:21

A Toolbar is just a collection of buttons and other controls. Clicking the button will fire an event that signals such, but it will not do whatever the button image says on it's own. You have to supply the code to Save, for example, or Save As, or change the Font of the selection and so forth. There is nothing that will do this for you.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

JDUK30-Sep-04 4:27

JDUK

30-Sep-04 4:27

If a user clicks on a cell in a dataGrid is there any way to return the row number of the cell they clicked (or double clicked) on?

Thanks.

Re: User clicks on dataGrid....

MarkMokris30-Sep-04 5:16

MarkMokris

30-Sep-04 5:16

This link gives an excellnet FAQ on the DataGrid.
http://www.syncfusion.com/FAQ/WinForms/FAQ_c44c.asp#q653q[^]

I believe question 5.12 shows how to do that.

Mark

Delegates, asynchronous invocation

Serge Lobko-Lobanovsky30-Sep-04 3:52

Serge Lobko-Lobanovsky

30-Sep-04 3:52

Hi everyone,

I've been stuck with this problem for several days already. My code extensively uses asynchronous delegate invocation using the Delegate.BeginInvoke method. The general pattern is as follows:

Scheduler or UI thread:
1) BeginInvoke function 1

First function:
1) prepare data
2) BeginInvoke data processing passing CurrentThread (see below)
3) CurrentThread.Suspend
4) (after resume) go to step 1 with new data processing command, if all commands are executed, exit

Data processing:
0) get calling thread (passed in parameters)
1) process data
2) set result
3) resume calling thread

Several data processing commands (Command pattern) require asynchronous calls, too. That is that BeginInvoke method is called from inside another method which was called using BeginInvoke, too. What I've noticed so far is that sometimes the delegate being BeginInvoke'd is NOT CALLED AT ALL! To give more evidence, I have a special Logger class which sends messages to a text box. Apparently, it uses Control.BeginInvoke to correctly dispatch Text property changes. Sometimes again the function specified in MethodInvoker delegate is also NOT CALLED AT ALL!

What could be the problem? I honestly hope it is not a bug in the framework, as the project is (and has been for the last month) in the final stage.

Regards,
Serge (Logic Software, Easy Projects .NET site)

Re: Delegates, asynchronous invocation

Dave Kreskowiak30-Sep-04 5:29