Whatâs the implication of putting a type in []?

BrianWren · October 31st, 2006, 06:29 PM

Found the following at: http://msdn.microsoft.com/library/de...erfactory.asp:

You can generate a new handler instance for ea. HTTP request by creating a class
that implements the IHttpHandlerFactory interface. In the fol. example, a
HttpHandler factory is used to create different handlers for an HTTP GET request and
an HTTP POST request. One of the handlers is an instance of a synchronous handler;
the other handler is an instance an asynchronous handler.

Code:

Imports System
Imports System.Web

Namespace Handlers
  Class HandlerFactory
    Implements IHttpHandlerFactory

    Public Function GetHandler(ByVal context    As HttpContext, _
                               ByVal reqType    As String, _
                               ByVal url        As [String], _
                               ByVal pathXlated As [String] _
                               ) As IHttpHandler _
                                    Implements IHttpHandlerFactory.GetHandler

        Dim handlerToReturn As IhttpHandler

        With context.Request.RequestType
            If "get" = .ToLower() Then
                handlerToReturn = New SynchHandler()
            Else
                If "post" = .ToLower() Then
                    handlerToReturn = New AsynchHandler()
                Else
                    handlerToReturn = Nothing
                End If
            End If
        End With

        Return handlerToReturn

    End Function
    Public Sub ReleaseHandler(ByVal handler As IhttpHandler _
                             ) Implements IHttpHandlerFactory.ReleaseHandler

    End Sub
    Public ReadOnly Property IsReusable() As Boolean
        Get
            ' To enable pooling, return True here.
            ' This keeps the handler in memory.
            Return False
        End Get
    End Property

  End Class
End Namespace

Register your custom HttpHandler factory by creating an entry in Web.config as follows:

Code:

<configuration>
  <system.web>
    <httpHandlers>
      <add verb="GET,POST" path="*.MyFactory" type="Handlers.HandlerFactory, Handlers" />
    </httpHandlers>
  </system.web>
</configuration>

What is the meaning of the â[String]â in the declaration of Public Function GetHandler()?

SQLScott · November 6th, 2006, 01:12 PM

I think it doesn't mean anything. I asked around to make sure and all the feedback I got was that:

ByVal url AS String

Is the same as:

ByVal url As [String]

If anyone knows otherwise, i'd like to know.

Scott Klein
Author - Professional SQL Server 2005 XML
http://www.wrox.com/WileyCDA/WroxTit...764597922.html

woodyz · November 6th, 2006, 05:53 PM

Square brackets are used to enable using reserved words or keywords as identifiers, which I suppose could somehow be useful.
I don't see how you could do that with String as in the example you posted. I looked at the link you supplied, and can't see any reason that would be needed there or why they used the brackets..

As an example of how they would be used (in the case where it was found to be of use): you would use square brackets to define a class that has a keyword for a name. Here, Alias is a vb keyword:

Code:

Public Class [Alias]
    Public Name As String
End Class

Then, wherever you use the class as a paramter, you use the square brackets as well to indicate you mean the class rather than the keyword:

Code:

Private Sub TestMe(ByVal s As [Alias])
    Debug.WriteLine(s.Name)
End Sub

Again - I see no use in the example from MS. But I could be missing something.

Woody Z http://www.learntoprogramnow.com

BrianWren · November 15th, 2006, 03:05 PM

I created a test app with this feature, built it, and then subjected it to ILDASM. I had two opposite declarations

Code:

    Public Sub S1(strVar1 As String, strVar2 As [String]) . . .
    Public Sub S2(strVar3 As [String], strVar4 As String) . . .

All for strings were handled in the representation in ILDASM exactly the same. The only difference was the number used to sequentialize them (I'm not referring to my sequentialization, but the compiler's).

Apparently this does nothing whatsoever, period.

Thanks for the input on it though.

woodyz · November 15th, 2006, 03:36 PM

Quote:

quote:Originally posted by BrianWren
Apparently this does nothing whatsoever, period.

I am glad you checked that. It is what I would have expected but haven't checked myself.

I can't see any way the actual purpose of square brackets (aliasing a keyword or reserved word) could be used on a type (such as String).

Woody Z http://www.learntoprogramnow.com