Create A Shared IEqualityComparer?
Jan 20, 2012
I'm doing some LINQ which requires a custom comparer, so I created a new class implementing IEqualityComparer. However, when I use it, I have to create an instance of it each time.
Dim oldListOnly = oldList.Except(newList, New MyEqualityComparer)
Dim newListOnly = newList.Except(oldList, New MyEqualityComparer)
I may be misunderstanding how .NET works, but it seems wasteful to create a new comparer each time. I really just want one instance (the equivalent of static in C++/C#).So I tried creating a "static" class, which in vb.net is a module. But got an 'Implements' not valid in Modules error.I then tried making the Equals and GetHashCode function shared methods on my class, but got this error: Methods that implement interface members cannot be declared 'Shared'.how to accomplish my goal here?
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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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Apr 8, 2009
I have the following function that loops through a directory and checks for a specified folder and file[code]...
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Jun 15, 2012
enter code hereWant to remove items from a Main list , but give an error 'Unable to cast object of type <ExceptIterator>d__99'1['
[Code]...
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Aug 5, 2011
I stumbled upon an article regarding the Birthday Paradox and it's implications when overriding the GetHashCode method, I find myself in a bind.In tests, we found that in calls to the ToLookup() Extension, only GetHashcode is used, despite providing the implementation for Equals.
I think I understand why this happens, the internal working of ToLookup, HashSet, Dictionary, etc, use the HashCodes to store and/or index their elements?Is there a way to somehow provide the functionality so that the equality comparison is actual performed using the equals method? Or should I not be concerned with the collisions? I haven't done the maths myself, but according to the first article I linked, you would only need 77,163 elements in a list before reaching a 50% chance of collision.
If I understand this correctly, an Equals() override that compares property by property such as
Return (a.Property1 == b.Property1 && a.Property2 == b.Property2 && ...)
should have a zero chance of collision? So how can I get my ToLookup() to equality compare this way?
In case you need an example of what I mean:
[Code]...
I can get that to work with an override of GetHashcode(), no problems. But I don't want to use GetHashcode because if I have, for example, 109,125 elements in my list, apparently I'm already at 75% chance of collision? If it used aforementioned Equals() override, I think I'd be at 0%?
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Jun 17, 2009
I am trying to implement a simple IEqulityComparer to use with LINQ collections. I have written the following code which is reduced to its simplest form for discussion purposes...
Public Structure bob
Dim SiteID As Integer
Dim fred As String
End Structure
[code]....
The problem that I have is that both functions throw the compiler warning "function 'getHashCode' (or 'Equals') shadows an overridable method in the base class 'Object'. To override the base class method, this method must be declared 'Overrides'."
However, if I declare them as Overrides, I get the error "function 'GetHashCode' cannot be declared Overrides because it does not override a function in the base class."!!I am also getting a compiler error on the "Implements" line to the effect that I must implement "getHashCode" but I presume that is a result of the first problem.
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Dec 31, 2011
I've created a Class Library using vb.net, the thing is that several applications should use this file.
I'm using Inno setup, and I'm declaring the dll file to be shared.
in the client app i've added refrence to the dll and set "Copy Local" to false.
Now if i put the exe file (the client app) in the same folder with the dll everything works correctly, but once I move the exe or use another application that should use the so called shared dll the assembly cannot be loaded because the system cannot find him ("IOFileNotFoundException")
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May 25, 2010
NetShareAdd API from a VB.NET application (.NET version 2.0) and although I can get the API to just create a basic shared folder I now want to create a shared folder and specify its Share permissions (not NTFS permissions) as well, which means I have to pass in a SHARE_INFO_502 structure rather than just a SHARE_INFO_2 like I was previously doing for creating a basic share. I have spent over 5 hours solid just trying to get this working and am getting to the point now where I really cant think of anything else to try.I've encountered several problems whilst trying to make this work but the one I am finally stuck on is this: When I call NetShareAdd it returns the error INVALID_PARAMETER and the parm_ err object (which is supposed to specify which member of the SHARE_INFO_502 structure caused the error) holds the value 501. I know it is something to do with the security descriptor because if I comment out the line where I set the SHARE_INFO_502 structure's shi502_ security_descriptor field then the code works without an error (just obviously does not set the share permissons I want).I think posting all of the code here might be a bad idea as its currently over 150 lines long (yes that is only code for getting this API working...) so I'll just post my definitions of the SECURITY_DESCRIPTOR structure and the code I am actually using to call the various APIs involved: [code] Each of those API calls prior to NetShareAdd returns a non-error value in the Debug.WriteLine that is done after each one, but there is obviously an issue somewhere with the security descriptor.
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Sep 3, 2009
I want to create an enterprise wide dataset so that my function will call this same dataset from any of the webpage. I've created shared code in the App_Code folder. In it, there's are dataset properties. Will the pages extract info from these dataset properties each time I call the shared program or will create new property for each page.I'm trying to emulate an Enterprise Java Bean type of coding.
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Jul 24, 2011
I like to create an extension method to Image.FromStream Public Shared Function FromStream(ByVal stream As System.IO.Stream) As System.Drawing.Image
With possibility to cancel processing like Public Shared Function FromStream(ByVal stream As System.IO.Stream, ByVal CloseTask As ManualResetEvent) As System.Drawing.Image
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Aug 3, 2010
I've been looking at using PROPERTIES [URL] but frankly I don't understand it that well. Before I invest the time to read, understand, and truly comprehend this, I want to make sure it's the best way. My intended goal is to create my database connection string in a function/sub somewhere, then assign it to this project wide string variable, then I can use it in any form, project wide without having to recreate it.
[Code]...
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Jan 12, 2012
Basically i am creating a vbnet system software. I want to create a shortcut key to lock the system with out affecting the windows explorer (just my system only). Is it possible to create one for that? Or let's say create a procedure that triggers anywhere whether the focus is on a control, on a form (whether shown as normal or modal), or on any other that has the focus on it.
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Jun 29, 2009
I am trying to work my way through the NerdDinner tutorial - and as an exercise I'm converting it to VB as I go. I'm not very far in and after having gotten past the C# Yield statement I'm stuck on Shared VB Array Initialisors.
static IDictionary<string, Regex> countryRegex =
new Dictionary<string, Regex>() {
{ "USA", new Regex("^[2-9]\d{2}-\d{3}-\d{4}$")},
[code].....
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Jun 28, 2009
I have products form and categories form here i am creating new products and categories both have its own id and also i need to create one sequential no for both depend on current year when i create new [code] also when i create new product i want its sequentialno to be same.1
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Jul 13, 2009
I have created a synchronized queue and am using SyncLock on the SyncRoot property of that queue when I invoke the Enqueue/Dequeue methods. The methods are invoked from instances of standard producer/consumer classes.Is that a proper use of the SyncRoot property?
Would it be better practice to create a private shared object in each class and lock on that instead?
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Apr 13, 2009
Using: Visual Studio 2005.We are developing three different applications. We currently have 4 different modules that we all share among our applications. When a change is made to one of the modules, we must make changes to the other two modules.If it is possible, how do you (where do you) create a single location for one file to be shared among three different applications? Hopefully this will avoid the unnecessay task of changing a file three times.
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Mar 1, 2012
I didn't write the function for the AutoCompleteExtender so I am not quite sure how to change it without screwing it up, so I figured I would ask here. Recently, it was requested that the AutoComplete show a product name & the date of launch of that specific product. I do not know how to add the date to the AutoComplete.
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Sep 30, 2010
Is it possible to create a folder on a remote machine that has no previously shared folders? I can do this...
vb
Dim fname As String = "\10.1.x.yDocumentsMyFolderName"
IO.Directory.CreateDirectory(fname)
[code].....
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Jan 27, 2010
I have an interface that i have declared some of the basic internal functions, subs, properties, etc. This interface is then implemented into 3 pre-defined classes. These classes are end-use classes so they dont get derived or inherited elsewhere. I am trying to create a generic shared class that can operate on each of these 3 predefined classes and potentially more as long as they implement the interface.
[Code]...
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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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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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Dec 16, 2009
is there a difference between shared events and non-shared events?
Private Shared Event EVENT_something_changed()
Private Sub SUB_handles_something_changed() Handles Me.EVENT_something_changed
End Sub
no errors with this code, but how is Me possible since the Event is shared. it seems like there's no errors between switching shared with un-shared and switching Me with Myclass, all 4 combinations seem to work, isn't that weird
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Jun 5, 2010
We have a system that makes a use of 3rd party COM DLL written in vba We have a centralised web application and 1-50 client machines that must reference that COM DLL in order to use our centralised web application.
The COM DLL is going to be updated rapidly in the future, which means that it has to be re-installed on every machine manually.Is it possible to centralise this COM DLL somwhere on the network? Is there any other alternatives? Otherwise the maintenance overhead will be huge.
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Mar 5, 2009
What is the use of shared variable in vb.net?
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Jun 12, 2011
I'm working on a voice recognition project in VS 2010. I'm trying to use SpInProcRecoContext instead of the shared one. However, I'm running into issue getting my program to recognize when I'm speaking. When I use the shared one I can make it work just fine. But with InProc it never picks up my voice. Right now it should just take what you say and put it into a text box. Here's my
VB
Option Explicit On 'Default ImportsImports SystemImports System.DataImports System.DeploymentImports System.DrawingImports System.Windows.FormsImports System.Xml 'Custom ImportsImports SpeechLibImports SIMPLEAUDIOLib Public Class frmMain 'Dimension variables Dim WithEvents RecoContext As SpInProcRecoContext 'The Main Recognition Object Used throughout the whole program.[code].....
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May 28, 2012
I am pretty new to multi-threading in general and I would like to know how can I lock a shared integer variable to not be accessed by other threads while it is read/updated by an other thread.When I try do do SyncLock myInteger, I get that error : Error 6 'SyncLock' operand cannot be of type 'Integer' because 'Integer' is not a reference type.
Here a simplified example of what I mean
Private Shared myInteger As Integer
Private Sub MySub()
SyncLock myInteger ' This does not work
' read/write a new value to myInteger
End SyncLock
End Sub
MySub is called by multiple instances of the class, and running in multiple threads?
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Jun 6, 2009
I'm looking at a VB.NET class (that I didn't write) that is declared "MustInherit" (abstract in C#, I believe) that has three methods, all of which are defined as "shared" (static in C#). There are no properties or fields in the class - only the three methods. From an OO perspective, does this make any sense?
My thinking is no, because by making it MustInherit, you're essentially saying you can't create an instance of this class - you must inherit from it and create an instance of the derived class. But since all the methods are shared, you'll never actually create an instance of the parent class anyway, so the "MustInherit" does no good. You might as well not mark it MustInherit and just inherit from it whenever you want.
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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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