.net - Extension Methods Error ?
Mar 7, 2011CODE:
View 2 RepliesCODE:
View 2 RepliesI'm trying to use PGK.Extensions in a T4 template in VS2008 for VB.NET and I get:
RemoveAllSpecialCharacters is not a member of string..
My T4 headers:
<#@ template language="VB" hostspecific="false" debug="true" inherits="Microsoft.VisualStudio.TextTemplating.VSHost.ModelingTextTransformation" #>
<#@ output extension="vb" #>
<#@ assembly name="PGK.Extensions.dll" #> // the dll is found
<#@ import namespace="StringExtensions" #> //Try with and without namespace
[Code]...
I would like to know your opinion on extension methods. Sure, it is a nice feature and makes you feel powerful. It's great to see your own method pop up when typing in a object. But it doesn't really add something new... You can get the job done with normal methods as well. I think extension methods do not belong in object oriented programming. It makes your code easier to read but harder to understand for someone else.
View 2 RepliesI'm trying to write 2 extension methods to handle Enum types.One to use the description attribute to give some better explanation to the enum options and a second method to list the enum options and their description to use in a selectlist or some kind of collection.You can read my code up to now here:
<Extension()> _
Public Function ToDescriptionString(ByVal en As System.Enum) As String
Dim type As Type = en.GetType
Dim entries() As String = en.ToString().Split(","c)
[code]....
So my problem is both extension methods don't work that well together. The methods that converts the enum options to an ienumerable can't use the extension method to get the description.
I wonder why it's impossible to create and extension method for Object? I use Excel PIA. The property Cells of Worksheet returns Object (if using with indexes). For example, Worksheet.Cells(1, 1) returns Object type. I know it's a Range object, and I want to cast it to Range. It would be convenient to write following:[code]
View 5 RepliesI know what extension methods are, how to create and use them, but I wanted to know more about how they actually work. How do they "attach" themselves to the type of object that you are extending? Or is there even an attachment being made. I know want to know more about the inner workings, etc.. I looked around and read several different blog posts about extensions and not one of them discusses how they actually work.
View 6 RepliesIf I try to call my extension method which is defined like this:
Module LinqExtensions
<System.Runtime.CompilerServices.Extension()> _
Public Function ToSortableBindingList(Of TSource)(ByVal source As IEnumerable(Of TSource))
[code].....
Code in VB.NET
[Code]...
works very well. So seems some consistency miss of the string constant behavior.
2) Have a look on the COMMENTS (in the attached picture). The words "custom", "string" and "error" are highlighted, however they are in the comments, so should be green, not blue.
Why this? What workaround? EDIT: Declared as "bug" in Microsoft Connect (even if is not more that a syntactic "miss")... EDIT 2: As remarked Hans Passant, standard string methods, like "cucu".Trim() does not work either.
Consider the following:
Public Module Extensions
<Extension()> _
Public Sub Initialize(ByRef Target as SomeClass, ByVal SomeParam as Something )
[code].....
Why is Case 1 failing to initialize the object as expected?
In VB.NET or C#, is there a way to determine if a class has been extended with extension methods?
View 3 RepliesIs there anyway to add an overload "extension method" to a method that already has one or more extension methods?For example theString.Contains method has two extension methods totalling 3 separate versions.Is there anyway to add an extra extension method also called "Contains" ?By the way I have tried it but the IDE does not seem to recognise additional EXTENSION methods where a method already hasone or more extension methods.Is there anyway around this restriction?In other words I would like to be able to change the Extension method below from"Contain" to "Contains" but it seems it is not recognised.
Option Strict On
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
[code].....
I made a library in C# and I've been told by people that one of mine methods don't work in VB.NET as extension [UR]
this is the method:
public static PropertyDescriptorCollection GetProps(this object o)
{
return GetProps(o.GetType());
}
I wrote some string extension methods in a VB assembly and am unit testing them from a C# project. However, C# acts like it cannot see the the extension methods, when other VB projects reference the VB assembly they have no problem. Both the VB assemebly and the C# test project are targeting .Net 3.5. Is there a way around this?
[Code]...
I have many similar calls to database and they work fine
Using ta As New QT_SSTEntities
Return ta.Product.
Select(Function(c) New RadComboBoxData() With {.Text = c.FieldName1, .Value = c.FieldName1}).
[Code].....
I'm using extension methods based on an array and I would like to know if there is an easy way to check that array got a specify size instead of me doing a copy paste of
if array.count != 1000
throw new exception "size of the array does not match"
in about ~50 extensions
this a small sample of extensions that I use, I got WAY more
<Extension()>
Public Function IsWhite(ByVal board() As bitPiece, ByVal pos As Integer) As Boolean
Return (board(pos) And bitPiece.White) = bitPiece.White
End Function
[code]....
Is it really impossible to create an extension method in C# where the instance is passed as a reference?
Heres a sample VB.NET console app:
Imports System.Runtime.CompilerServices
Module Module1
[code].....
I have the code as below:
Dim xdTest As XDocument = XDocument.Load(GetXMLPath())
Dim objResult = From xe In xdTest.Elements("Some Element") _
Where xe.Element("strName").Value = strInput _
Select xe.Element("intValue").Value
objResult.
I cannot access any extension methods for objResult, like .ToList() or .First(). The file imports System.Linq and the project is targeted to .NET 3.5. How do I get the extension methods back?
I have a project written in MVC2 and VB.NET. I use a lot of htmlhelper extension methods,and I have them all in a public module. They work just fine, and I can compile and run my project. I reference the namespace they are in with this:<%@ Import Namespace="MyProject.WebUI.Extensions" %>So, again, they work great, my project runs and compiles without a hitch.The problem is that each one of these extension methods is shown as an error:
Error 33 'TabbedMenu' is not a member of 'System.Web.Mvc.HtmlHelper(Of Object)'. C:ProjectsMyProjectMyProject.WebUIViewsSharedSite.Master 23 21 MyProject.WebUI
[code]....
I have a number of very useful extension methods that I'd like to use in my Silverlight project.I've pasted the Module here [URL]The problem I'm having is that visual studio complains that the dlls my module have been written against have not been built against the Silverlight runtime.Is there an easy way to get these extension methods working in Silverlight?I'm thinking my main hurdle is getting IObjectSet and ObjectContext to run against the Silverlight run-time - perhaps there's another way to expose these methods that I'm not aware of.
View 1 RepliesI am trying to write extension methods in VB.NET
Imports System.Runtime.CompilerServices
Module ExtensionMethods
<Extension()> _
[code]....
But I am getting this error.Class 'System.Web.UI.WebControls.ListItem' cannot be indexed because it has no default property
What could be wrong?I am calling the code like this.
ddlSalesmanager.Items.FindByText(survey, StringComparison.CurrentCultureIgnoreCase)
P.S: I ported this wonderful code from C# to VB
The code I want to work:
<Extension()>
Public Function NValue(Of T)(ByVal value As Nullable(Of T), ByVal DefaultValue As T) As T
Return If(value.HasValue, value.Value, DefaultValue)
[code].....
I have a very specific problem concerning Dns.GetHostEntry.A service uses Dns.GetHostEntry to retrieve all IP Adresses of a host, using the name of of the host. This has always worked fine. At a specific customer, Dns.GetHostEntry throws the "no such host is known" error when querying specific hosts. The problem only occurs when trying to resolve hosts that are on a different domain than the machine the service is installed on. The service has worked for quite some time, but recently is stopped working, throwing the "no such host is known" error (sadly, no stack trace is available). Nslookup works though, no problems there.The service in question is written in VB.NET, targetting the .NET Framwork 2.0.The comments in the MSDN entry for .NET 3.0 (http:[url]....aspx indictate that there may be a problem with the reverse DNS entries for the hosts, but I was not able to reproduce the problem on a test network, even with all reverse lookup zones deleted (there are more comments for other .NET Versions, all having similiar problems). [EDIT:] Even deliberatly addind a wrong PTR record does not make the problem occur on my test machine.[EDIT2:] The only thing that made the error come up was disconnecting the network adapter, and thereby making the DNS Server unavailable, even though the forward resolving still worked due to caching.So, my questions are: Under which conditions does GetHostEntry throw this specific error? Which resolution methods does it use? If I'm not mistaken it uses the unmanaged WinSock function getnameinfo (http:[url]....: "Name resolution can be by the Domain Name System (DNS), a local hosts file, or by other naming mechanisms".Any ideas why this suddenly fails for machines on the other domain (but not for machines on the same domain)?
View 1 RepliesThis is the original code in c#
public class CategoryRepository: RepositoryBase<Category>, ICategoryRepository
{
public CategoryRepository(IDatabaseFactory databaseFactory)
: base(databaseFactory)
[Code]...
Does anyone has an idea what i should change to let it work and let my UserRepository use the methods in RepositoryBase while implementing the IUserRepository?
I am using following code to get a directory of files with a particular extension. It throws an error that you donot have administrator privileges.
CODE:
I am using the .getdirectory to scan my whole c drive for certain files to be backup. e.g *.doc. however when i run the code, i hit into error. stating folder access error. one of the folder which cause the error is system information volume.
View 8 RepliesWhy would I use an extension method instead of just creating non-extension sub or function?
For ex, I could have an extension function called IsNullOrEmptyOrAllSpaces on String, which does a check as its name implies. Or I can write a stand alone function that does the same thing. Other than having the extension show up in Intellisense, is there any advantage? Is a call to the extension quicker/more efficient than a call to a regular function?
I m selecting the folder & playing all the files in the media player, of that folder. As u know folder contains all types of files including text,zip,image & so on. So I want that when URL that is assigned to Media Player is .txt,then i assign any default image from resources. I do not want to check extensions- Currently I m checking the extension of each file before paying but i dont want dat.
[Code]...
I am working with a vb program, but there is something strange on one of my .vb code pagewhen i put the "dot" afther the object name its dont show the methods availables for this objectbut on other vb code pages i can see it. but in this one no.for exmaplethis is a piece of code: Dim sb As New StringBuilder()
View 3 RepliesI am not sure how clear my question is by the title, but I am trying to make Class methods instead of Instance methods in Visual Basic that way I don't have to waste memory and code creating temporary objects to execute methods that don't need instance variables.
I am not sure if you can do that in VB but I know you can in Objective-C by using either a "+" or "-" sign in front of the method declaration. And in C++ (at least I think, I can't remember) you put the static keyword or const keyword in front of the function.How would I do this in VB if it is possible? Or should I just make a separate set of functions that are not members of a class?
I saw this post and I want to know if this is possible in VB. So like extension method, do extension properties exists in VB.Net? Here I've read they do, but cannot find any examples.
View 3 Replies