I have an application which was built a few years ago. I came across a section of code that baffled me as the functionality this provides throughout the ASP .Net application is great but i just dont understand it. Perhaps its the [] throwing me off but i think it could be some C# code converted to VB .Net.... Not sure but wondered if anyone understands this and if so could they share what its doing
The code in an NotInheritable class
Public Overloads Function [Get](Of B)() As B
Dim myType = GetType(B)
Return DirectCast([Get](myType), B)
End Function
I understand it overloads a function but
Why are the [] there for and what do they mean? When would you use them? If i remove them i have a compiler error.
Get in VB .Net is used in properties so is this some shortcut access to a property somewhere? Or
where could i view which method its overloading?
I've used code similar to List(Of Customer), IQueryable(of Customer) but how has (Of B) allowed in this manner?
I have read up on MSDN and researched around. The only thing that comes to mind is either some C# syntax conversion or some old VB6 syntax which the original developer must have used whilst creating the application.
Appreciate any clarification on this.
Because Get is part of Visual Basic Language Keywords. You need the bracket to indicate you want to use them as a method/property name.
Here is an excerpt from Microsoft on Keywords as Element Names in Code (Visual Basic):
Any program element — such as a variable, class, or member — can have
the same name as a restricted keyword. For example, you can create a
variable named Loop. However, to refer to your version of it — which
has the same name as the restricted Loop keyword — you must either
precede it with a full qualification string or enclose it in square
brackets ([ ]), as the following example shows.
1) Brackets allow you to use reserved words as identifiers (like the ampersand in c#).
2) It appears to be a bad naming decision. If they wanted to hide an existing member they could have used the Shadows keyword.
3) You'll need to examine the inheritance hierarchy. Start with the most recent parent.
4) It is calling a different overload of Get in the implementation but the Of B is trying to contrain it to B for some reason.
Related
I always work in C#, but I've been asked to work on a legacy VB.Net solution. In the legacy code, I am seeing this:
Private transactionListField() As TransactionInfoForStatement
This makes no sense to me! If it was C#, I'd expect this:
private List<Transaction> _transactions;
Can someone please explain to me what that VB code does? The parenthesis after the name makes me think it is calling a method, but when I Go To Definition in Visual Studio, I just end up on the same line!
That's an array declaration, you could also use this syntax that i prefer:
TransactionListField As TransactionInfoForStatement() ' array which is declared but Nothing
Arrays or indexers always use () in VB.NET as opposed to C# where you use [].
There's one advantage if you use the braces-first-syntax, you can specify the size:
TransactionListField(10) As TransactionInfoForStatement ' array that contains 11 Nothing
While using Revit API and browsing the "RevitAPI.chm" file (and browsing examples on the internet), I have noticed that some methods exist while not being listed neither in the "RevitAPI.chm" file nor suggested when using RevitPythonShell.
I explain. Let's say for instance that I have a "Space" Object, obtained with
s = FilteredElementCollector(doc).OfClass(SpatialElement).ToElements()
If I do, let's say (assuming s[0] is a valid Space object):
s[0].Geometry
I got an 'indexer object':
<indexer# object at 0x0000000000000049>
But if I do:
s[0].get_Geometry(Options())
Then I got my GeometryElement object. The same behavior goes with get_BoundingBox, for instance.
Now, that's fine, but the only way I could know about these get_something methods is by seeing examples (either on the "RevitAPI.chm", or on forums etc.). So that's kind of strange, isn't it? In the sense that these methods aren't actually listed.
So I guess my questions would be:
Is it the normal behavior? (or should I normally just get a GeometryElement object by using s[0].Geometry, for instance?)
If yes, ... why ? :D
What are these 'indexers' ?
Thanks!
Arnaud.
PS: Using Revit 2017, tests made with RevitPythonShell and pyRevit
The methods prefixed by a lowercase get_ are automatically generated getter methods. The official Revit API provides and documents the BoundingBox property on the Element class. Rather inelegantly, this so-called property takes an argument. Therefore, the C# .NET implementation generates a property getter function for it.
VS 2013, MVC 5, VB, Entity Framework
This is part of my Class:
Public Class Order
....
Private mFirstName As String
<Required(ErrorMessage:="First name required - hard coded")>
Public Property FirstName() As String
Get
Return mFirstName
End Get
Set(ByVal value As String)
mFirstName = value
End Set
End Property
....
I want to setup a resource file to allow error messages to change with different countries. What would I write to have the error message pulled from a resource file named ErrorMessages.resx?
The examples for doing this are mostly in C#, and finding the VB equivalent was difficult, at least for me, and I thought other VB programmers might appreciate the proper syntax.
The C# answer is:
[Required(ErrorMessageResourceType=typeof(ErrorMessages),ErrorMessageResourceName="FirstNameRequired")]
What was difficult was to find the proper VB operator to apply for the C# "typeof" operator. In VB the line above is:
<Required(ErrorMessageResourceName:="FirstNameRequired", ErrorMessageResourceType:=GetType(Resources.ErrorMessages))>
in the lines above, the Name/Value pairs are stored in ErrorMessages.resx (see how to create below), and "FirstNameRequired" is the Name of the string that will hold the actual text to be displayed.
Just to cover the bases:
What's pretty neat is that VS2013 automatically creates the Class and type definitions for the resource file and they show up in Intellisense, as in the VB line above 'Resources.ErrorMessages'.
It's also important to note the Data Annotation operators can have only one or the other of the two error message string properties, so the property "ErrorMessage" had to be removed as seen in the code lines in this answer post.
To use a Global Resource file (local files are possible), on the project node do an Add > Add ASP.NET Folder > Add App_GlobalResources. Then inside that folder Add > New Item > Resources File. After that the Name-Value pairs can be added, and then later additional country-culture resource files can be added, and online documentation for this process is fairly plentiful. ASP.NET, and MSDN for the country-culture.
The MSDN page that lists all of the data annotations is here; But I didn't find enough code samples to readily explain how to take advantage of the properties listed.
Hope this is helpful for someone else.
Best Regards,
Alan
I have a byte[] and wanna convert it to object parameter in asp.net.
byte[] version =98471574580;
and I have One method that wants "ObjectParametere version".I must convert byte[] version to
ObjectParametere.
The way to do this has a few steps that if you follow in future shoudl save you needing to ask this sort of question again.
1) Look at the documentation for the class you want to use. It is found here: http://msdn.microsoft.com/en-us/library/system.data.objects.objectparameter(v=vs.110).aspx googleing for "ObjectParameter" returns it as top hit for me. Google might have noticed me doing a lot of MSDN searches though and bumping them to the top so if in doubt try adding MSDN or c# to the search.
2) Look for how to create an instance of the object. This would usually be through constructors. Sometimes you may use static methods but constructors are usual and in fact there are two here we can consider.
3) Decide which constructor to use. One takes a name and a type. One takes a name and a value. Since we have a value this seems like the one to choose.
4) Call the constructor you have decided to use and assign it to a variable (or use it directly in your code). In this case the syntax would be var objParam = new ObjectParameter("version", version);.
Some of these steps might be short circuited. For example if you are programming in Visual Studio then typing new ObjectParameter( should then offer intellisense help on what constructors are available, saving the need to look the documentation up online.
I obtain a HTTPCookie, but need a Net.Cookie. Are they just something you can recast, or how would i go about it?
Actually you have two questions:
Difference between System.Web.HttpCookie and System.Net.Cookie
How to convert from HTTPCookie to a Cookie.
Part 1)
This question is really interesting ,I'm still thinking why there are two classes which looks pretty same ,My initial thought was System.Web.HttpCookie inherits System.Net.Cookie but this isn't true both directly inherit from Object so they are distinct classes ,but the properties matches a lot ,so this gives a hope for the solution of part 2.
Part 2)
I think its possible to convert one into another theoretically since both are just objects if you populate them the right way it will work , here a little analysis when I compared the two classes.
Click to open in new tab to enlarge
Update:
The System.Web is made to be used in server-based apps and System.Net can be used for client based apps.
Some Thoughts:
Write a method or a static class which can convert one object into another, I haven't check all of them but properties whose names match, there signature also matches.
Properties which don't exists in the another object you can stuff some constant or a value which you know matches the scenario like Port number.
Good luck ,let me know how you came up with the final solution ,post the code or link.
Some Links
this post has some related code