Re: What's the point of Remoting if you need to "Add Reference" - C# Discussion Boards

Re: What's the point of Remoting if you need to "Add Reference"

17-Aug-03 22:20

One question, What's the point of Remoting if you need to "Add Reference" -- if you need to add reference (to gain access to assembly meta data), then why bother going thru layers of overhead with remoting? Just package your code in a class library dll and on the client side, just instantiate the object - no need to Activator.GetObject. Just:

MyObj obj = new MyObj();

I think I am missing something here. okay, remoting lets you run your remote object in a separate process/app domain but anything besides that?

Thanks!

norm

James T. Johnson18-Aug-03 3:27

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 3:27

There isn't much of a point if you have to include the server implementation with the client. But it is possible to split it up so you'd have 3 assemblies:

Shared - contains interfaces or base classes implemented by "Server"
Server - references "Shared" and implements "Shared" assembly's interfaces or base classes
Client - references "Shared"

If you want a ton of information about remoting you should get Ingo Rammer's book, Advanced .NET Remoting. I'm on Chapter 4 now and I've been really impressed with it. You can get chapter 2 from his website[^] which covers the basics of remoting, while chapter 3 shows some caveats to what was shown in chapter 2 and offers ways through and around them.

Chapter 4 so far is concentrating on how to use configuration files to get around having to hard code everything in the server/client.

James

"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

devvvy18-Aug-03 5:20

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 5:20

oooo... there're too many books that I need to read in too little time....

life's short, ....

anyway, QUOTE:

Shared - contains interfaces or base classes implemented by "Server"
Server - references "Shared" and implements "Shared" assembly's interfaces or base classes
Client - references "Shared"

QUESTION: so, basically, you have two dll and two exe:
1. RemoteObject.dll
2. Interface assembly of remote object (RemoteObjInterface.dll)
3. Server (RemoteObjServer.exe):
a. References the interface assembly (2)
b. Register channel, register type.
4. Client (RemoteClient.exe):
a. References Interface assembly (2)
b. Do you still use Activator.GetObject()?

Just thinking how to implement interface.. By the way, you still need to refernce interface assembly. I guess the point of remoting is that RemoteObject do run in different process/app context/server - meaning it has access to resources on a remote server (database/file/AD/registry...etc). if it wasn't that, there's not much of a point for remoting (am i missing something here?)

norm

James T. Johnson18-Aug-03 5:44

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 5:44

norm wrote:
Do you still use Activator.GetObject()?

Yes/no, for certain remoting scenarios you use it; in other cases you can use configuration files and some generated wrappers to get around it.

norm wrote:
meaning it has access to resources on a remote server (database/file/AD/registry...etc). if it wasn't that, there's not much of a point for remoting (am i missing something here?)

Another use is to have a single place to keep your code up to date. For example, you could use remoting to host a business rules library or data access library. If rules change you can update the assembly on the server but not have to update each client.

Another would be to simply keep your code from even being on the client computer. This is similar to the web service approach, but you don't have to host through a web server.

James

"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

devvvy18-Aug-03 6:51

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 6:51

Thanks. But I'm having some trouble separating interface with remote class. Calls to:

SERVER SIDE:
RemotingConfiguration.RegisterWellKnownServiceType(
typeof(nsCRemoteObj.CRemoteObj), //QUESTION 1: I still need to reference the remote object - as opposed to the interface??
"CRemoteObjURI",
WellKnownObjectMode.SingleCall //QUESTION 2: Since we'll be communicating with client via "interface", NO Singleton?
);

AND

CLIENT SIDE:

IRemoteObj obj = (IRemoteObj) Activator.GetObject(
typeof(CRemoteObj), //QUESTION 3: Opps, I still to reference the remote object assembly - in addition to interface assembly!??
"http://localhost:8085/CRemoteObjURI"
);

Any idea?

**********************************************************************
code structure below if you're interested. (Questions are highlited --> "QUESTION"):

(1) my remote object source file (CRemoteObj.cs) (dll):

using nsCRemoteObjInterface; //For IRemoteObj interface.

namespace nsCRemoteObj
{
public class CRemoteObj : System.MarshalByRefObject, IRemoteObj
{
... some stuff ...
}
}

Then, "add reference" to reference the interface assembly (CRemoteObjInterface.cs).

(2) Interface assembly (CRemoteObjInterface.cs) (dll):

using System;

namespace nsCRemoteObjInterface
{
public interface IRemoteObj : IMarshal
{
bool AuthenticateLoser(string sUserName, string sPasswd);

};
}

Nothing needs to be referenced from interface assembly.

(3) Server "CRemoteObjServer.cs" (exe):

{

[STAThread]
static void Main(string[] args)
{
//Register channel:
TcpServerChannel tcpchannel = new TcpServerChannel(8086);
ChannelServices.RegisterChannel(tcpchannel);

HttpServerChannel httpchannel = new HttpServerChannel(8085);
ChannelServices.RegisterChannel(httpchannel);

//Register TYPE:
RemotingConfiguration.RegisterWellKnownServiceType(
typeof(nsCRemoteObj.CRemoteObj), //QUESTION 1: I still need to reference the remote object - as opposed to the interface??
"CRemoteObjURI",
WellKnownObjectMode.SingleCall //QUESTION 2: Since we'll be communicating with client via "interface", NO Singleton?
);

Console.WriteLine("CRemoteServer started and listening on tcp(8086) and http(8085).");
Console.WriteLine("Hit any key to exit.");
Console.WriteLine();

Console.ReadLine();

}

(4) Client "CRemoteObjClient.cs" (exe):

using nsCRemoteObj; //QUESTION 3: Still need to reference remote object assembly in addition to interface assembly...
using nsCRemoteObjInterface;

namespace nsCRemoteObjClient
{
class CRemoteObjClient
{
[STAThread]
static void Main(string[] args)
{
//Register channel:
ChannelServices.RegisterChannel( new HttpChannel() );

try
{
//Retrieve remote object proxy (WellKnown object - server-activated SingleCall):
IRemoteObj obj = (IRemoteObj) Activator.GetObject(
typeof(CRemoteObj),
"http://localhost:8085/CRemoteObjURI"
);

//Invoke function thru proxy:
Console.WriteLine("CRemoteObjClient: Client side invoke.");
bool bAuthStatus = false;
for(int i=0; i<3; i++)
{
bAuthStatus = obj.AuthenticateLoser("Paul", "12345");
Console.WriteLine("i={0}, bAuthStatus: {1}", i.ToString(), bAuthStatus);
}

}
catch(Exception err)
{
Console.WriteLine("Exception: {0}", err.ToString());
}

}
}
}

norm

James T. Johnson18-Aug-03 11:27

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 11:27

Q1: Yes, you publish the object implementing your shared interface
Q2: No, you can use Singleton mode as well as SingleCall
Q3: You don't have to reference the server assembly, just the shared assembly because your client code should look something like:

try
{
  //Retrieve remote object proxy (WellKnown object - server-activated SingleCall):
  IRemoteObj obj = (IRemoteObj) Activator.GetObject(
    typeof(IRemoteObj), // <-- Note the change from CRemoteObj to IRemoteObj
    "http://localhost:8085/CRemoteObjURI"
  );
...

The Type passed in is simply to tell the Activator what type of object it should marshal back and forth between server and client. Your specific object is specified by the second parameter which includes the name for that object.

Hope that makes some sense,

James

"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

devvvy18-Aug-03 15:07

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 15:07

Okay, it's working now, thanks a lot!

On server side:
RemotingConfiguration.RegisterWellKnownServiceType(
typeof(nsCRemoteObj.CRemoteObj),
"CRemoteObjURI",
WellKnownObjectMode.SingleCall
);

On client side:
RemoteObj obj = (IRemoteObj) Activator.GetObject(
typeof(IRemoteObj),
"http://localhost:8085/CRemoteObjURI"
);

One more QUESTION: Alrite, we're using interface. Just why however, we can only use server-activated, and NOT client-activated?

norm

James T. Johnson18-Aug-03 15:26

Re: What's the point of Remoting if you need to "Add Reference"

18-Aug-03 15:26

norm wrote:
Just why however, we can only use server-activated, and NOT client-activated?

When you're using an interface a client-activated method would require you to do:

IRemoteObj obj = new IRemoteObj();

But you can't create an instance of an interface. So in order to use a CAO it would require you to switch from using an interface to using a base class, the downside to this is that the CAO won't let you use non-default constructors. And then it gets worse... Typically your base class is declared as abstract, but if the class is abstract then you can't use the new operator again because you can't create instances of abstract classes.

As you can see, it is rather confusing. That is why I highly recommend picking up Ingo's book, because it lays out a lot of this information for you. I don't have the book in front of me, but I think a lot of chapter 3 focuses on this topic.

James

"My words but a whisper -- your deafness a SHOUT.
I may make you feel but I can't make you think." - Thick as a Brick, Jethro Tull 1972

devvvy18-Aug-03 18:05

Where r the Shape and Line Controls???

18-Aug-03 18:05

Thanks a lot.

norm

pShay17-Aug-03 21:43

pShay

17-Aug-03 21:43

Back in the good old VB6 there where the Shape and the Line controls, which were very useful. They seemed to disappear in the VB7 and the C#. Does any one know what happened to them?

Re: Where r the Shape and Line Controls???

Sascha Andres17-Aug-03 23:27

Sascha Andres

17-Aug-03 23:27

dshay1 wrote:
Does any one know what happened to them?

AFAIK they disappeared by design. That is that you must paint your own line with GDI+. I don't think this is a great shift back. One may think about creating a control that behaves similar to the VB6 controls. Besides they were easy to use, they had one big caveat: They were full blown objects, with all the memory consumption.

Try searching codeproject.com for examples on GDI+. You will find how to draw a line - and four lines make a shape Wink | ;)

Sascha

--
http://www.livingit.de
http://www.mobile-bookmarks.info

Re: Where r the Shape and Line Controls???

Ista18-Aug-03 16:59

Ista

18-Aug-03 16:59

In the words of ME

THANK GOD

just use the GDI+ its more reliable on exact positions than those controls ever were

I'm not an expert yet, but I play one at work. Yeah and here too.

exposing remoting from ASP.NET

devvvy17-Aug-03 20:37

17-Aug-03 20:37

I am just reading up on remoting, and I figure it'd nice to be able to expose remoting object thru web service. Unfortunately, the book i'm reading have very little information on this. The following is what I do know, hope someone can add to that:

1. Server side:
a.create virtual directory
b. modify web.config to add remoting configurations, such as <wellknown...>
c. make sure assembly of remoting object is under /bin directory of the virtual directory.
d. make sure IIS is running.

QUESTIONs:
1a. Do we need to create a "WebService" to host this remote object? I understand ASP.NET is responsible for channel registration and web.config has the information on what remoting object is hosted. But anything else in addition?
1b. Web.config:
<wellknown mode="SingleCall"
type="XXX.YYYYY.MyRemoteObjClass, MyRemoteObjClassAssemblyName",
objectUri="RemoteObjAssembly.soap"
/>

1b-1. What's objectUri?? Why is it not:
"http://localhost/MyRemoteObjClass.dll" instead?
1b-2. Why "soap" file as opposed to a dll?
1b-3. How can you create this SOAP file?? Do you have to script it yourself?
1b-4. MyRemoteObjClassAssemblyName is the "assembly name" --> meaning, "file name" of the assembly of remote object class? In the assembly info file, there's [assembly: AssemblyTitle("")], but nothing that you can do to specify "assembly name".

2. Client side:
a. create a client app (C#, win app, console app, anything)
b. configure remoting by configuring client's application config file. Specify what remoting object you wish to connect to.

For example: ClientApp.config
<configuration>
<system.runtime.remoting>
<application>
<client url="http://localhost/MyVirtualDirName"> //QUESTION 2b-1: What if there're more than one assembly in the virtual directory?
<wellknown
type="XXX.YYY.MyRemoteObjClass,
MyRemoteObjClassAssemblyName"
url="http://localhost/MyVirtualDirName"
/>
</client>
</application>
</system.runtime.remoting>
</configuration>

QUESTION 2-b-2: Do we need to "Add-web-reference" or just "add reference" to the assembly of Remote object class (MyRemoteObjClass.dll)??

QUESTION 2-b-3: I understand that for remoting/ASP.NET, we only get stateless wellknown or server-activated objects --> So, we get to instantiate the object with either:
MyRemoteObjClass obj = (MyRemoteObjClass) Activator.GetObject(typeof(MyRemoteObjClass));

Or

MyRemoteObjClass obj = new MyRemoteObjClass();

QUESTION 2-b-4: Do we need "using XXX.YYYY" in our client application to reference namespace used in remoting object class?

Question 3: Okay, this's a silly question, but what the difference between URI and URL?

RemotingConfiguration.RegisterWellKnownServiceType(typeof(MyRemoteObjClass), "MyRemoteObjURI", WellKnownObjectMode.SingleCall);

What's "MyRemoteObjURI"? I thought a URI is like an URL:
"http://127.0.0.1/MyRemoteObjURI"

Doesnt a URI contains: "protocol alias" + "domain name/IP" + "resources identifier" (which is MyRemoteObjURI" in this case)?

That's a lot of questions, thanks for going over them.

norm

"as" keyword in C#?

devvvy17-Aug-03 20:06

17-Aug-03 20:06

Hi, just going over some code, came across this:

object[] channelData = or.ChannelInfo.ChannelData;
foreach(object data in channelData)
{
...
ChannelDataStore dataStore = data as ChannelDataStore; //QUESTION: "as" keyword - what does it do?
...
}

I thought in C#, unlike in VB, we don't "as". If we need to cast, we do this:

ChannelDataStore dataStore = (ChannelDataStore) data;

THanks.

norm

Roger Alsing17-Aug-03 20:10

Roger Alsing

17-Aug-03 20:10

i should not swear on this but i think this is how it works.

if you do

bla var=(bla)some_other_var;

you will get an error if "some_other_var" is null

but if you do:

bla var= some_other_var as bla

it will accept null values to , (i think , ive not tested this but i think i saw that somewhere)

//Roger

J. Dunlap17-Aug-03 20:17

J. Dunlap

17-Aug-03 20:17

What if data cannot be casted to the type ChannelDataStore? What would happen is there would be an error, and you wouldn't be able to trap the error. So the makers of the C# language included this keyword, so that the variable would become null if casting failed, rather than throwing an error.

"Blessed are the peacemakers, for they shall be called sons of God." - Jesus

"You must be the change you wish to see in the world." - Mahatma Gandhi

devvvy17-Aug-03 20:39

17-Aug-03 20:39

Thanks guys.

norm

Russell Morris18-Aug-03 4:30

Russell Morris

18-Aug-03 4:30

As others have mentioned, casting will throw an error if the cast is invalid. The 'as' keyword will never throw an error - it will return 'null' if the cast is invalid.

MyClass myClass;
object otherObject;

myClass = otherObject as MyClass;

is logically equivalent to the following:

MyClass myClass;
object otherObject;

if( otherObject == null || !typeof(MyClass).IsAssignableFrom(otherObject.GetType()) )
  myClass = null;
else
  myClass = (MyClass)otherObject;

--
Russell Morris

"So, broccoli, mother says you're good for me... but I'm afraid I'm no good for you!" - Stewy

devvvy18-Aug-03 5:11