Custom Generic.IEqualityComparer(Of T) - Compiler Errors
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 13, 2011
Cookies to be stored in folder and on close delete the cookies The ability to watch youtube vids, view images, and play js/flash games good security, no ads?
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Sep 25, 2009
which compiler errors would be detected out by VB compiler?
I have searched out some compiler errors list for C#, for example, see the website at [URL]
MS provided us the information about C# compiler error. Does MS provide VB compiler errors information as well.VS
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Oct 7, 2010
I have the following code:
Dim compiler As ICodeCompiler = New Microsoft.JScript.JScriptCodeProvider().CreateCompiler
Dim params As New CompilerParameters
params.GenerateInMemory = True
[code].....
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Jul 22, 2011
When I try to compile my project, I get this error
Error 1 Unable to copy file "objDebugoneForce.pdb" to "binDebugoneForce.pdb". Access to the path 'objDebugoneForce.pdb' is denied. oneForce.
How to rectify it? [URL]
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Sep 23, 2011
I have a .net application that uses customerrors web.config module to display meaningful messages for errors. It works without any issues for 500 errors/exceptions caused by non-ajax and ajax components (updatepanel). However, in a scenario where updatepanel's asynchronous request times out, there is no error raised at all. I was able to see the timeout in firebug and come up with a solution that would at least display the error message as an alert and then redirect the user to the 500 error page using javascript but it's not quite doing what the rest of the application does in case of an unhandled errors like these. I basically just want everything to go through "LogEvent" mechanism so based on the severity of the error, it does the necessary work.This 500 error page doesn't have anything in the Server.GetLastError() for these timeout scenarios. Is this an expected behaviour? Can it be changed so I do have access to these timeouts in Server.GetLastError() OR maybe just run this error through "LogEvent" mechanism? Is there a better/more graceful way to handle this issue?
Below is my code to give you an idea, not exactly what I have in my application but pretty close.
Web.Config
<customErrors mode="On" defaultRedirect="~/Errors/ErrorUnknown.aspx" redirectMode="ResponseRewrite">
<error statusCode="500" redirect="~/Errors/Error500.aspx" />
</customErrors>
[code]....
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Mar 24, 2010
Here's my Application_OnError event sink in global.asax.vb:
Sub Application_OnError(ByVal sender As Object, ByVal e As EventArgs)
Dim innerMostException As Exception = getInnerMostException(Me.Context.Error)
[code].....
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Dec 8, 2010
How is conditional compilation controlled for a VisualBasic web? For a VB Windows app, I put a conditional variable in Project > Compiler tab > Advanced > Custom controls.
How in a VB web app is a conditional compilation variable assigned that can be accessed by all the files of the web app?
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Jul 20, 2011
When I am Connecting a website through remote machine, The Website showing the run-time error
Details: To enable the details of this specific error message to be viewable on remote machines, please create a tag within a "web.config" configuration file located in the root directory of the current web application. This tag should then have its "mode" attribute set to "Off".
Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's configuration tag to point to a custom error page URL.
But i want to display entire site in my website, and one more thing i am using Ajax controls in website, they are CalenderExtender control.[code]...
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May 17, 2012
I'm an amateur programmer who's learned quite a bit from online references, and usually searching eventually reveals the problem but I'm stuck!I've overcome many obstacles when creating a custom button on the Ajax Editor control, namespace issues, registring the controls properly etc. I resist the temptation to ask for help because the errors should lead me in the right direction. Now I get no errors, but the control isn't visible! The tag is in the .ASP page and I even set the width, height and visible tags in case it's being hidden but nothing shows up.
[Code]...
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Mar 24, 2011
i have created a new DataTable with some Numeric Columns and bound the data to a Datagridview dtFCData.Columns.Add(iC.ToString, System.Type.GetType("System.Double")) The Users of the Application can now edit values in this Column. If they enter not numeric text and confirm it, the default Error Message is Displayed. How can i replace this ugly Errormessage by my own message?
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May 10, 2010
I created two classes. One class is StudentClass and the other is HomeroomClass. The HomeroomClass contains a readonly property as a generic list of the StudentClass. [code]...
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Jan 1, 2011
Here are essential excerpts for the code creating the class and the page using it:
Imports System.Collections.ObjectModel
Public Class Test (Of T as xyz)
Inherits Collection (Of T)
[code].....
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Feb 25, 2009
I wrote a class which imports System.Collections.ObjectModel. For the management of the collection, I've written:
Default Public ReadOnly Property Item(ByVal vntIndexKey As Integer) As ItemType
Get
Return CType(mCol.Item(vntIndexKey), ItemType)
[code].....
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Dec 22, 2009
To the point: I need to transfer a custom object's event through a generic collection object containing these items so that any class using the collection can see that changes were made to one of the items in the collection.
I.E. An item event that triggers a collection event
[Code].....
Due to the application requirements, I need the Collection and Items to send immediate notice of various changes that occur to the Collection Class and its items. I've already got my events set-up regarding for the Collection Class, but I'm struggling with coming up with a workable solution for raising events for the items.
I've got an event for the DeviceLayer item set-up, but how do you transfer that event through the CollectionClass so that any other class using it will see that there was a change to one of the items in the collection?
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Nov 11, 2010
Imports System.CodeDom.Compiler
Public Class iCompiler
Public Shared Sub GenerateExecutable(ByVal Output As String, ByVal Source As String, ByVal Icon As String)[code].....
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Jun 19, 2009
I have several custom classes in a VB.NET (VS2008) project which are related to each other through generic list collections. The lower tier classes refer directly to some of the parent classes (to make it easier to refer backwards up the chain). My question is, is it possible to add the reference to the parent class when the item is added to a collection, when that collection is a property?
Below is some sampling of code to illustrate.
Public Class FlexServer
Private m_FlexLicenses As List(Of FlexLicense)
Private m_Modules As List(Of FlexModule)
Public Property FlexLicenses() As List(Of FlexLicense)
[code] .....
In the code above I have the FlexServer class which refers has two lists as properties, one for FlexLicense and one for Modules. The FlexLicense class has a property to refer back to the FlexServer class that "owns" it. In order to update this property in code, I have to add the FlexLicense to the FlexServer.FlexLicenses list AND set the FlexLicense.FlexServer property. What I am looking for is, is there a way (in the property definition or wherever) to both add the item to the list and alter it at the same time?
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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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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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Dec 16, 2009
We have migrated our Vb6 application to VB.NET using a third party tool. Now we are in a process of Refactoring and introducing object oriented concepts in the application.
In VB6, we were using structures in many places. As a part of introducing object oriented programming,
1. is it a good idea of changing all Structures to Classes? or Is there a concept of "Generic Structure" similar to Generic collections, Generic classes?
2. Can some one guide me any source containing guide lines or best practices for applications that are migrated to VB.NET from VB6 and implementing object oriented programmaing.
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Apr 7, 2011
it seems always at this time I cant figure out how to do something maybe it has something to do with lunchtime.
Im having trouble using a method that is defined by an outside company
This is a link to their integration guide:
[URL]
This is their documentation for the class Im trying to use
OrderQueryWebService Class
This class is for SID in particular and is made for use with the notification methods. This is for the Order Query Web Service specifically, allowing clients to return the status of transactions for their merchant, whenever they want to.
Methods
/ <summary>
/ Pass through the variables required and receive a list of Transaction
objects showing transaction status
[Code].....
The MerchantCode, the MerchantUsername, the MerchantPassword are all good the List is a custom type called SetComHash.Transaction
Everytime I try adding a string to the list such as the transactionNumber and some other values it gives me a type error:
"Value of type string cannot be converted to 'SetcomHash.Transaction'
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Jul 1, 2011
This error first appear to occur randomly. Steps to recreate:Open Visual Studio and load a solution (some files automatically opened) - this is when the problem occurs Close all open files Restart visual studio and load solution (no issues)Open Exactly the same files again, restart visual studio and load solution so files open automatically (problem occurs!)
However, when trying to narrow it down to a single file (that is automatically opened when the solution is loaded), I couldn't reproduce the problem. Now with all the files open again the problem doesn't occur!!! So it looks like it is fixed - though this happened before and eventually the issue came back.
I think it is to do with one of the user controls with DevExpress controls on it - when the error occurs, the designer displays the error. Though I can't reproduce it at the moment to confirm that.
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Feb 9, 2012
If I look at the IL that is created in Linqpad for the two following code snippets, I wonder what happens here.
In c#
int i = 42;
results in the following IL code
IL_0000: ret
whereas in VB
Dim i As Integer = 42
it is
IL_0000: ldc.i4.s 2A
IL_0002: stloc.0
Apparently, the c# compiler understands the the value is never used and thus simply returns nothing. In VB.NET the actual code is translated.Is that due to differences in compiler optimization or is there anything else at work?
Update: Just to clarify this - I just enter this one line into LinqPad and look at the IL it creates (most definitely by running the respective compiler). There is no program.
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Apr 13, 2012
Consider:
Public MustInherit Class Column
Public ReadOnly Property ReturnSomethingUseful() As Object
Get
'return something useful
[code]....
But this gives the following error:
Public Overrides Function ParseValue(sValue As String) As Boolean'
cannot override 'Public Overridable Function ParseValue(sValue As String) As Object'
because they differ by their return types.
I accept that you can't do this, but I'd like to be able to preserve the semantics of what I'm. trying to do, which is to have an untyped version that deals with Object, but a typed version in derived classes that knows about the specific type T.
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Aug 14, 2010
I have a Journal that records entries for different types: Journal(Of ParentT)
[Code]....
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Nov 25, 2011
I am trying to construct a generic interface class with generic functions. My goal was to use this to implement multiple worker classes for database interaction that have the same basic functionality. Each class will deal with different object for example, category, product or supplier but unless the the functions in the interface are generic that this won't work.This is the interface code that I have but I don't know if I have done it correctly. [code]
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Jul 7, 2010
I have created a Dictionary class (MyDictionary for the example). I am currently trying to pass MyDictionary into a function, filter it into a new instance of MyDictionary and pass this new instance into another method. When I am attempting to create the second instance from the filtered first instance of MyDictionary via Lambda Expressions and the ToDictionary Method, I am getting the following error:
Unable to cast object of type 'System.Collections.Generic.Dictionary`2[System.Int32,System.String]' to type 'MyDictionary'. I have simplified the example and recreated it in LINQPad and am getting the same error.
Here's the simplified version of my code:
[Code]...
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Jun 30, 2011
I am trying to create a list of a generic type in vb.net 2.0 framework.
This is the generic type definition:
Public Class GenericParamMap(Of T)
Public Sub New(ByVal pParamName As String, ByVal pPropValue As T)
mParamName = pParamName
[Code]....
The compiler does not allow a "T" in the method's parameter because it's not defined, but I'm not sure how or where to define it. I thought it was okay to have a generic method definition.
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