Static variable related query c#

Question

2.50/5 (4 votes)

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.NET2.0

Hi,

I have a C# class in .net 2.0 in which I want to use the variable(static int) whose values is set in one method which is static and that variable is used in another static method.

The value of that variable changes according to some condition.
That variable must have only two values 0,1 from if else for true and false.

I have declared a static int type variable in that class which is global and both methods can use that, but I got an exception 'object is not reference to object'.

Also value once assign will not change in future assignment.

thanks.

Posted 15-Mar-11 1:37am

Balwant.mnd

Updated 16-Mar-11 12:13pm

Dalek Dave

v2

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Comments

Albin Abel 15-Mar-11 7:58am

Static variables belongs to a class, it can't have multiple memory locations like instance variables. So It is not belongs to each instance and can't access through instance of an object. Look my answer for an example

fjdiewornncalwe 15-Mar-11 13:59pm

OP Comment moved from answer:
thanks
but i m asking?
can static variable be incremented in any method and new value is used by another method.

Niklas L 15-Mar-11 14:44pm

yes (in your case)

Albin Abel 15-Mar-11 14:46pm

The static variable can be incremented. It sustain till the process live (Windows application). If you have a static variable (in a class apart from page) in a web application it sustains till the web server shut off. So care need to be taken in web app that it should not hold high load unless otherwise needed. Now answer for the question, Is new value is used by another method. If you are asking the new value= incremented value then Yes!. If you are asking about assign a new value then Yes!. Static variable also like other variables, but just its scope not belong to a particular instance. is it clear now?

Dalek Dave 16-Mar-11 18:13pm

Edited for readability.

4 solutions

Solution 6

Additional instructions: how to report the problem properly. You need to create full exception dump and look at exception stack to point out code lines where exception is being propagated. Please see my directions:

How do i make a loop that will stop when a scrollbar reaches the bottom[^]
When i run an application an exception is caught how to handle this?[^]

When you do it, you will find out where the exception is. If you still cannot solve the problem yourself, post relevant extra information, but only in this way: use "Improve question" and proper formatting.

—SA

Posted 16-Mar-11 10:21am

Sergey Alexandrovich Kryukov

v2

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Albin Abel · Accepted Answer · 2011-03-15T01:56:00

Solution 1

Static variables not referenced through an object instance.

For example public class Car{ public static int noOfWheels{get; set;} } will be get or set by Car.noOfWheels=4; and not by Car car=new Car(); car.noOfWheels=4;. The later throw exception

Posted 15-Mar-11 1:56am

Albin Abel

Comments

fjdiewornncalwe 15-Mar-11 13:59pm

+5, correct.

Albin Abel 15-Mar-11 14:37pm

Thanks Marcus Kramer!

Sergey Alexandrovich Kryukov 15-Mar-11 20:26pm

All you say is correct, but OP's case is something else because exception is mentioned. It only happens in run-time. We need source code.
--SA

Sergey Alexandrovich Kryukov 15-Mar-11 20:27pm

Balwant, show you source code and exception, point out in each line. So far, you got some correct statements, but probably not the Answer to your problem. This is only because you did not share enough information.
Please reply to my comment.
--SA

Albin Abel 16-Mar-11 8:48am

Hi SAKryukov OP posted a code snippet. But I see this code fragment not complete. May be you have look and predict the problem?

Sergey Alexandrovich Kryukov 16-Mar-11 16:17pm

Well, I added my Answer as a supplement advice on "only two values 0, 1", but there is absolutely no matter to suggest any help on the main problem.

Balwant, what's wrong? Why not dumping full exception info and find our and post _relevant_ code?

--SA

Sergey Alexandrovich Kryukov 16-Mar-11 16:23pm

OK, I added my second "Answer" but in fact directions on how to obtain proper report of the problem and post it properly.
Balwant, you need to follow these directions and then post more info.

Please notify Albin as well by replying to this comment.

How about that?
--SA

Balwant.mnd 16-Mar-11 0:43am

public class dept
{
public static bool CETresult;
//some of the statements related to class not depends on CETResult variable
//below is the main code which set the value for this static variable.
for(i=0;i

Espen Harlinn 16-Mar-11 18:04pm

Nice effort - my 5

Dalek Dave 16-Mar-11 18:14pm

Good Answer.

Espen Harlinn · Accepted Answer · 2011-03-16T12:08:00

Solution 7

Why didn't somebody just say: yes

Best regards
Espen Harlinn

Posted 16-Mar-11 12:08pm

Espen Harlinn

Comments

Dalek Dave 16-Mar-11 18:14pm

YES!!!!! :)

Espen Harlinn 16-Mar-11 18:22pm

Thanks Dalek :)

fjdiewornncalwe 16-Mar-11 23:01pm

I'd say yes if she was cute enough...

Espen Harlinn 17-Mar-11 9:39am

Thanks Marcus!

Albin Abel 16-Mar-11 23:02pm

Yes! Yes

Espen Harlinn 17-Mar-11 9:40am

Thanks AlbinAbel!

Manfred Rudolf Bihy 17-Mar-11 10:46am

Yes!

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-03-16T10:14:00

Solution 5

A side dish: if you need some type with values 0 or 1 only, this is what you should do:

C#

enum Discrete : byte { Low = 0, Hight = 1, } //for example

It will force writing correct code at compile time but won't prevent other values during run-time (the fact which can be used to the benefit as well).

[EDIT]
Why not boolean? There are important applications for that. Here is the example. Imagine a numeric calculation using or not using certain special factor. What to do? Using "if (useSpecialFactor) //..."? Nah! Look:

C#

enum SpecialFactorUse { Ignore = 0, Use = 1, } 
//...
double Calculate(SpecialFactorUse specialFactorUse /* */) {
   //...
   return mainFactor + specialFactor * (int)specialFactorUse;
}

//...

enum Direction { Left = -1, StayHere = 0, Right = +1, } 
//...
Direction direction = getNewDirection(currentDirection, arrowKeys);
//...
double newPosition = currentPosition + step * (int)direction;

—SA

Posted 16-Mar-11 10:14am

Sergey Alexandrovich Kryukov

Updated 16-Mar-11 12:30pm

v5

Comments

Espen Harlinn 16-Mar-11 18:07pm

Nice idea - 5ed, but I wonder why he isn't using a bool -> " 0,1 from if else for true and false"

Sergey Alexandrovich Kryukov 16-Mar-11 18:29pm

Because OP did not want bool :-)
No, quite serious, using enumeration is different. Please see my updated Answer above -- pretty interesting...
Did you use such techniques? I find it handy, use from time to time, since Object Pascal and Delphi (maybe even Turbo Pascal). Huh?
--SA

Espen Harlinn 16-Mar-11 18:51pm

Well, I believe I do :) Those where the days - mapping sets of enums to integer falgs
TEnum = (One,Two,Three) - TEnums = Set Of TEnum, Flags array[TEnum] of Integer ... etc :)

Sergey Alexandrovich Kryukov 16-Mar-11 19:19pm

Yes, set of enum was great. I address the sets a bit on my article on C#/.NET enum.
--SA

Albin Abel 16-Mar-11 23:04pm

The Enum idea is a good advice. My 5

Sergey Alexandrovich Kryukov 16-Mar-11 23:06pm

Oh, thank you. Did you see my articles on enumerations? My three last articles?
--SA