Is the virtual keyword really necessary? - C# Discussion Boards

Niiiissssshhhhhuuuuu27-Oct-06 4:20

27-Oct-06 4:20

I want to create one bluetooth application which can send commands to a robot which is having a bluetooth receiver.I am clear till the application that sends the bt signals to robot but from receiver side what should I do?Can Any one tel me.How can I do programming there in C#.

nishu

Invoke Constructor method of any class that extends an Interface without having to specifically cast each class

Jost Pedro27-Oct-06 4:14

Jost Pedro

27-Oct-06 4:14

Hi guys,

I have a class that extends an IMenuProvider interface and belongs to a plug-in project. In the UI project(other project) I've developed a menuService class that finds plug-ins that implement a IMenuProvider interface and execute the constructor method by using the invoke method. Here's the code.

<code>...

 Type[] types = assembly.GetTypes();
            foreach (Type type in types)
            {
                if (type.GetInterface("IMenuProvider") != null)
                {
                    if (!ht.ContainsKey(type.FullName))
                    {
                        //get construct info.
                        ConstructorInfo cinfo = type.GetConstructor(System.Type.EmptyTypes);
                        
                        //invoke constructor 
                        IMenuProvider imp = (IMenuProvider)cinfo.Invoke(null);  **
                        ht.Add(type.FullName, imp);
                        RegisterProvider(imp);
                    }
                }
            } 
...
</code>

So what happens is the line marked with ** returns an error saying "Unable to cast object of type 'TestPlugin.PluginMenuProvider' to type 'Enki.UI.ComponentModel.IMenuProvider'."

I know that I’m attempting to invoke the constructor method of the subclass PluginMenuProvider through the extension IMenuProvider but i don’t want to have to specify every subclass that extends the IMenuProvider interface.
Now, my question is how can i invoke the constructor without having to declare and than cast each class type that extends the interface IMenuProvider like the line marked with ** does?
Best regards.

Pedro M.

Re: Invoke Constructor method of any class that extends an Interface without having to specifically cast each class

led mike27-Oct-06 5:25

led mike

27-Oct-06 5:25

Jost Pedro wrote:
execute the constructor method by using the invoke method

Invoking constructors might have a place but I would avoid it. From a design perspective I would use a Creational Design Pattern.

led mike

Re: Invoke Constructor method of any class that extends an Interface without having to specifically cast each class

MGoettmann27-Oct-06 6:18

MGoettmann

27-Oct-06 6:18

Pedro,

have a look at Plug-ins and cast exceptions [^].

Martin

Re: Invoke Constructor method of any class that extends an Interface without having to specifically cast each class

S. Senthil Kumar28-Oct-06 4:11

S. Senthil Kumar

28-Oct-06 4:11

How about simply using Activator.CreateInstace[^] instead, especially considering that the constructor doesn't take any parameters? That's the typical way in which objects are created using reflection.

Type[] types = assembly.GetTypes();             foreach<span> (Type type </span>in<span> types) </span>            {                 if<span> (type.GetInterface(</span>"IMenuProvider"<span>) != </span>null<span>) </span>                {                     if<span> (!ht.ContainsKey(type.FullName)) </span>                    {                          IMenuProvider imp = (IMenuProvider)Activator.CreateInstance(type);
                         ...

Regards
Senthil [MVP - Visual C#]
_____________________________
My Blog | My Articles | WinMacro

getting current logged-in user name of windows

saqib8227-Oct-06 3:36

saqib82

27-Oct-06 3:36

Hi how to programmatically get the name of the user who is currently logged-in to the windows.

regards

sAqIb

"Our scientific power has outrun our spiritual power. We have guided missiles and misguided men."
Dr. Martin Luther King Jr.

Re: getting current logged-in user name of windows

Eric Dahlvang27-Oct-06 4:00

Eric Dahlvang

27-Oct-06 4:00

System.Environment.UserName

--EricDV Sig---------
Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them.
- Laurence J. Peters

Is the virtual keyword really necessary?

Shy Agam27-Oct-06 3:07

Shy Agam

27-Oct-06 3:07

Hey all,

I have an abstract class which defines some functions, WITHOUT declaring them virtual.
When I derive from that class, I simply use the override keyword and declare the same signature for the function.
It works perfect AFAICT...

Is there any place we are forced to use the virtual keyword?
Is it wrong not to use it?
Does it break the polymorphism rules?

Thanks in advance,
Shy.

Re: Is the virtual keyword really necessary?

Rob Philpott27-Oct-06 4:14

Rob Philpott

27-Oct-06 4:14

That's weird. In order to be able to mark a method with override the base class method must be either itself override, abstract or virtual.

... or on my compiler it does anyway.

Regards,
Rob Philpott.

Re: Is the virtual keyword really necessary?

Shy Agam27-Oct-06 4:19

Shy Agam

27-Oct-06 4:19

I do declare the functions as abstract...
Just not virtual.

Re: Is the virtual keyword really necessary?

Rob Philpott27-Oct-06 4:31

Rob Philpott

27-Oct-06 4:31

ah ok. virtual is implied from abstract, as an abstract method can't have an implementation, one must be supplied by each child class.

If it wasn't implicitly virtual, you'd not be able to call the method on a base class reference.

Regards,
Rob Philpott.

Re: Is the virtual keyword really necessary?

Guffa27-Oct-06 4:34

Guffa

27-Oct-06 4:34

An abstract method is also automatically virtual.

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b { font-weight: normal; }

Re: Is the virtual keyword really necessary?

Shy Agam27-Oct-06 4:36

Shy Agam

27-Oct-06 4:36

Oh... I see...
Thanks guys...

HAND...

Parameterized transactions & non-parameterised transacions

Haseeb Mukhtar27-Oct-06 2:58

Haseeb Mukhtar

27-Oct-06 2:58

Hello all,

What will be benefit if we use parameterised transactions for inserting, updating records.

For a large scale development which should be better the simple sql complete query based solution or parameterized solution.

Re: Parameterized transactions & non-parameterised transacions

Dustin Metzgar27-Oct-06 8:38

Dustin Metzgar

27-Oct-06 8:38

You might want to check out this article: SQL Injection Attacks[^]

Logifusion[^]

ABT C#

sanki77927-Oct-06 2:18

sanki779

27-Oct-06 2:18

Hi
i am new to the world of C# and previously have worked on C++ and C. i have made certain applications using c# but i am not confident on it. Whats the Best way to do learn c# in shortest time?
PLz help Cry | :((

Thanks
Sankalp Verma

Re: ABT C#

ed^nrgc27-Oct-06 2:20

ed^nrgc

27-Oct-06 2:20

Since you already have a grasp on C++, C# is mostly going to be a search for the correcet namespace. I would recommend a book from Wrox or OReilly on your subject of choice. Keep in mind that Windows (Winforms) and ASP.NET as very different animals. Same syntax, just many different namespaces.

Re: ABT C#

sanki77927-Oct-06 2:47

sanki779

27-Oct-06 2:47

Thnaks for that idea but there are hell of things in C# like WMI , web based applications ADO.Net ADSI etc and its hee that i get confused that what shall i do?
My main work area is Networking and we need to write script files based on windows.can you tell me is C# the best language to do so or shall i go for WSH or VBS?????

Sankalp Verma

Re: ABT C#

ed^nrgc27-Oct-06 2:59

ed^nrgc

27-Oct-06 2:59

I may be wrong, but I believe most networking is done in VBS.
There are several articles here that may help you in c# or C++:

http://www.codeproject.com/cs/system/cstcpipwmi.asp
http://www.codeproject.com/dotnet/adduseracetofile.asp
http://www.codeproject.com/w2k/adsiuserdmo.asp

Re: ABT C#

Kevin McFarlane27-Oct-06 4:02

Kevin McFarlane

27-Oct-06 4:02

For finding equivalents to the Win 32 API this may help:
Microsoft Win32 to Microsoft .NET Framework API Map[^]

Jesse Liberty's Programming C# is pretty good for ex-C/C++ developers.

Also see his C++ -> C#: What You Need to Know to Move from C++ to C#[^]

Kevin

Re: ABT C#

Kevin McFarlane27-Oct-06 4:07

Kevin McFarlane

27-Oct-06 4:07

Apart from the links in my other post see here:

http://samples.gotdotnet.com/quickstart/[^]

Kevin

Re: ABT C#

Rahithi27-Oct-06 10:50

Rahithi

27-Oct-06 10:50

hi verma,
we r sailing in the same boat. i am also new to C#.
it is better to do some sample appliations which are related to real time applications.
and work practically each and every concept of C#.
already u r into C++ (into Object oriented Programming), so u should not worry much about C#.
i saw one site,and felt to good for one who is new to C#. it is csharp-station.com.go thru the each and every lession in the Tutorial. and work on their samples.
this site(i mean www.codeproject.com) is also very usefll for us. in
General C# sections, u will find C# Samples. they are really good to learn C# coding standards.
all the best,
rahi

a few questions about C# and internet explorer ?

cmpeng3427-Oct-06 1:49

cmpeng34

27-Oct-06 1:49

hi all,
i want to ask a few questions about controlling internet explorer with C#:

* let's assume i am using IE7:

1. (if my browser is open)
- how can i change the first tab's url ? (assume there are a few open tabs)
- how can i add a new tab & open a url ?

2. (if my browser is not open)
- how can i start ie7 with and url ?

* let's assume i am using an older version of IE

1. (if there are a few open IEs)
- how can i change the first IE's (first one on the TaskBar) url ?
- how can i open a new IE with a url ?

thanks in advance, bye.

MFA

Re: a few questions about C# and internet explorer ?

rah_sin27-Oct-06 2:07

rah_sin

27-Oct-06 2:07

u acn try

System.Diagnostics.Process.Start("http://www.msn.com");

it will open the site in default browser of ur system.

rahul

Re: a few questions about C# and internet explorer ?

Niiiissssshhhhhuuuuu27-Oct-06 4:03

Niiiissssshhhhhuuuuu

27-Oct-06 4:03

HI,

Use this.

process1.StartInfo.FileName="iexplore";
process1.StartInfo.Arguments="NishuSoft.com";
process1.Start();

Which browser you want to use..give its exe file path.....Aand try....

Cool | :cool:

<marquee>nishu

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