Shared Variables And DLL Usage
Oct 20, 2011
I'm trying to split some prior crafted code into a DLL. It's a simple logger system.There are a few things that need to be shared with the main form in the project, so I set them up as a shared variable, but I don't use shared stuff often, and I worry it will cause variable conflicts regarding scope. I figured I would make a post here about it and see if someone can explain what I don't fully understand.Since this is a logger it will be used a couple of places. Other DLLs that need logging may reference it through a instanced object and project reference. My main form will also have an instanced object and a reference to the logger libary.Since one of my properties is a connection string and it's shared, does this mean that a instance of my logger class inside a DLL will have the same shared values as a instance on my main UI form? Or will the fact that the instance is inside of a DLL provide the scope boundary I need?
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Jun 4, 2010
I am trying to add shared members in derived classes and use that values in base classes...
I have base
class DBLayer
public shared function GetDetail(byval UIN as integer)
dim StrSql = string.format("select * from {0} where uin = {1}", tablename, uin)
end function
end class
[Code]..
currently there is error using the tablename variable of derived class in base class but i want to use it i dun know other techniques if other solutions are better then u can post it or u can say how can i make it work? confused...
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Jan 18, 2011
I have a problem with inherited classes. Have a look at the following VB.NET 2.0 / VS 2005 code:
MustInherit Class templateclass
Public Shared x As String
End Class
Class child1
[code]....
The templateclass has a shared variable x which is of course inherited by the child classes. But I wonder that all child classes share only one x! Until now I thought that shared variables are only shared among the instances of a class, not among all childs. This is very annoying because I have a base class which I need in two slightly different versions and they should not "share the shared" variables. And because the classes have a lot of shared variables, shadowing each in the childs would be very..
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Mar 13, 2012
I was reviewing the MSDN documentation on VB.Net's little-used Static keyword for local variables. My question is not about how Static works (I personally plan to avoid using it as it seems like it could cause grief to future programmers who don't notice the side-effects.) My question is about this statement in the docs:[code]So can anyone interpret the above statement for me in a way that makes sense? Or is this a bug in the documentation? It's been there since the VS 2005 version of the docs and is still present in the Visual Studio 11 version.
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Jul 23, 2009
I am making a small application in which i have added a class module and a window forms in vb.net. i want to acess the shared variables and mathods of class without making any object.
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Jun 22, 2009
exact diff b/t Static v/s Shared variables in VB.NET?
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Nov 29, 2009
basically i was wondering if we could inherit shared variables but restrict its scope to only that of the class itself.
Class A
Public Shared shared_variable as Boolean = true
End Class
[code]....
when i do this A.shared_variable = False, B's shared_variable also becomes false. how do i stop this?i cannot remove the Shared keyword because shared_variable should be able to be accessed without an instance of the class?
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Feb 21, 2012
I've been doing some reading on garbage collection in .NET and I was hoping for some clarification. So, as I understand it if I declare a public shared class variable, the GC will never get rid of it. Is this correct?Also, what then of private variables? Take the following example:
public class myClass
private shared myString As String
public sub ChangeString(newString As String)
[code].....
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Mar 12, 2012
So I am currently attempting to wrap my head around create multi-threaded programs and I am currently running into an issue when using a Shared variable across multiple threads.The program is structured as follows: Public Shared IsActive as Boolean
Main Thread = GUISets the Value of IsActive through a Button ControlTwo Worker ThreadsBoth threads are while loops that read the IsActive Boolean Ex:While IsActive = True Do Work End WhileHowever when I change the value of IsActive from the Main Thread it causes the worker threads to stop (ThreadState = 16).
I have been reading that I have to synchronize/lock shared resources and have tried SyncLock and Monitor methods without success (it is entirely possible I am not using the above correctly, so If someone could provide proper examples for the above situation using the mentioned methods please share them).
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Feb 15, 2009
I have created a public shared subroutine in a class file in asp.net 2 (vb.net) web site app_folder.The subroutine retrives some values from a sql database via an sql query and assigns the datareader field values to several variables The problem is I can't seem to assign the variables from the subroutine to the variables and textbox controls in the asp.net page I am calling the subroutine from. The textbox text value just appear blank.By the way, if I response.write the variables in the subroutine they appear populated by the sql data reader.
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Jul 31, 2010
Are the following three the same upon compilation
dim x as new assigningfunction
dim x as new assigningfunction()
dim x as assigningfunction = new assigningfunction()
[code].....
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Apr 23, 2012
Public Shared _formRef As frmMain
Public Shared f As frmMain
Class Server[code].....
but once firing off the code i get the error you see in my image attached.
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May 19, 2011
Well I am a new to VB.NET, converting a legacy system to .NET world. Recently I have been reviewing the already existing code since I joined the project quite late in the team. I find that there are many shared functions (not shared class) inside many classes. I doubt this may create some problem if two requests ( i.e two different HTTP request to the same method as it's a WCF application, of course exposed methods are not shared but internally called methods are shared) comes to the same shared method and both the calls to the method may have different method parameters/arguments, overwriting each other's arguments. In short, if shared method has a list of arguments which is going to be processed, is there any chance of inconsistencies in the light of multiple access to the shared method via two http requests.
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Jul 22, 2009
give me a good resource that explains the difference between a Private, Public, Shared Functions/Sub/Variables? I normally use Public for Subs/Functions inside of Modules I call from other parts of the program. But I'd like to get more of an understanding of how and when to use them. I want as little as impact to a system that is running my programs as possible, so i guess the key here is I'm trying to just get more proficient in my coding.
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Jun 8, 2009
I came across a number of new Private Shared variables (of type Hashtables(Of String), initialized in the declaration) added to a partial class for a very large (DataContext-derived) class. This seems sensible to me in one sense because they never change, and making these shared variables ensures that they won't get re-initialized every time a function is called. However, these variables are only used within the scope of one function in the class, and I fear the private namespace of this DataContext-derived class is getting rather polluted, and having these sorts of things exposed at such a high level might be confusing to others reading the code in the future.
Would there be negative performance impact to making these local variables within the function where they are used, or is there some better way to handle this? Basically we are using these 3 hashtables to determine whether anything within particular subsets of properties changed (using GetModifiedMembers and then using the Overlaps function of the hashset to see if any of the modified members correspond to members we care about).
Edit: I caved and took the time to write my own test program, which confirmed that there is a cost to using local variables (which I assume applies generally to all cases -- I doubt there's any case where a shared variable would be slower unless using the shared variable requires some additional logic to do so properly): [Code]
So in this particular case, using the local variable costs about 200%. But in most cases (including my own), the time is probably negligible compared to the overall task. So I guess the question now becomes, how do people generally feel about improving code maintainability at the cost of negligible but known performance impacts?
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Sep 30, 2011
I am writing some code that uses fixed regexs to search strings and pattern match. Its simple stuff, but I want to improve regex performance with compiling (its a high traffic website). I was thinking of compiling the regex and putting it in a Shared (static) variable inside a class. Something like this:
[Code]...
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Dec 8, 2011
I have the following class which I want to serialize to XML:
[Code]...
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Aug 23, 2011
Will the list in this shared method keep its state throughout the life of the method? Or will a new list be created every time this method is called?
[Code]...
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Dec 28, 2009
I've found out that if two instances of an SSRS report run at the same time, any Code variables declared at the class level (not inside a function) can collide. I suspect this may be the cause of our report failures and I'm working up a potential fix.The reason we're using the Code portion of SSRS at all is for things like custom group and page header calculation. The code is called from expressions in TextBoxes and returns what the current label should be. The code needs to maintain state to remember what the last header value was in order return it when unknown or to store the new header value for reuse
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Jan 25, 2010
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Aug 25, 2011
I have a class like this:
[Code]...
It works, when I make getBar methods public, but I don't want to expose these unneccessarily. Why I can't call private shared methods from a public one in the same class is over my head. I'm using .net framework 4.0 in a web application.
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Mar 30, 2012
I've taken over the maintenance of the website (ASP.NET VB) and on one particular page I noticed the below code
Inherits System.Web.UI.Page
Public Shared UserNumber As String
Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
[Code]....
My question is whether the variable UserNumber can be accessed or changed by any other user than the current one?
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Aug 12, 2009
Given in the following language specification, for me at least, calling Db.Foobar() [In the following code] does not indeed call off to the Shared Constructors of the base classes. I am curious as to a) is this my own fault for doing something wrong or b) is this an error in the language specification[code]...
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Jan 14, 2011
I seem to be drawing a blank. I'd like to create a "shared" variable that is shared with all instances of a class but not classes that inherit from it. For example.Class A: Shared list As New List(Of String): list.Add("A")
Class B Inherits A: list.Add("B")Class C Inherits B: list.Add("C")The end result I'd like is that any instance of A has just A in the list. Any instance of B has A and B in the list. Any instance of C has A, B, and C in the list. I can accomplish it by creating Instance variables, but I have to construct the list for each instance of a class. I'd like to construct it once for a specific point in the Hierarchy and then share it accross other instances of that class.
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Dec 11, 2011
Last year (2010) I came across a FANTASTIC command that allowed me to take a string of variables with a common delimiter and break it all back out into separate variables (possibly an array) with one statement.
[Code]...
As long as the delimiter was a unique specifiable character, this one-statement command could break it out into elements. my memory and point me in the right direction.
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Sep 27, 2010
I have code, shown below, that works all except for 1 thing: The variables being passed byRef get passed, but once modified in the else section of the "if me.invokerequired" code of RecordData, the variables are never updated in the calling function. To reiterate, the calling function does not receive the updated data that is in the variables custid and amt.When debugging, I see the data change in the else section of "if me.invokerequired", but once it returns from the callback the data is missing.[code]
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Mar 23, 2012
I define some global variables of a class as follows:
Private Class MyClass
Private var1 as Decimal
Private list1 as List(Of string)[code].....
But I found that after this form is closed, all above variables, var1, list1, list2 still exist in memory. I thought they should be collected by gc since the form is already disposed as I confirmed.
Add: I have monitored half an hour after the form is closed. But these variables are not collected by gc. I have an automatic update procedure on the form which uses above variables.Since the above variables still hold values, the automatic update procedure is always called which causes exception. (One quick fix is to check if form.isDisposed in update procedure. But I do not think this is elegeant. Besides, these variables occupy memory.)
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Jan 7, 2010
Does the memory used in declaring variables are reclaimed by the OS when these variables go out of scope?Does the memory used be released by setting thier value to nothing? if not, then how can I force the garbage collector to run or excecute at a certain/desired time..How about in Windows Forms..How can we make sure that the memory used in initializing and showing forms be released if those forms were closed?
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Mar 8, 2011
Question 1: What is the difference between "Background Worker" and "Worker Pool" as indicated within the MSDN samples provided.
Question 2: I noticed while using, AddressOf _Function_, variables cannot be passed; what would be an efficient solution to this?
Question 3: While using multithreading is it required to invoke before setting variables, or only form properties?
Question 4: While using System.Net.Sockets is it safe/efficient to use Application.DoEvents while waiting for new data; or would be using a Do While loop be fine without DoEvents since the action would be multithreaded? Note: there can be up to 2000-3000 sockets in use at a time.
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Jun 9, 2012
I'm new in .NET programming.I have a class Form1 that includes Button1_Click event.Button1_Click creates a multiple Text Boxies at run time)Here is the class:
Public Class Form1
Dim shiftDown As Integer
Dim counter As Integer
[code].....
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