C# Discussion Boards - CodeProject

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

Re: Problem whit loops :x

18-Aug-03 5:11

That's the best explaination i have seen today. Thanks.

norm

My Network Places

Nick Seng17-Aug-03 17:04

Nick Seng

17-Aug-03 17:04

Does anyone know how to list the content of this folder? I've tried using the System.IO.Directory class to no avail.

God, I pity me! - Phoncible P. Bone

If I end up Windows ME someone is going to be hurting. - One of the answers to a question for What OS are you

Re: My Network Places

Mazdak17-Aug-03 19:48

Mazdak

17-Aug-03 19:48

Just a gues, maybe you can do it with System.Managgement. There are some classes for Network in WMI.

Mazy

No sig. available now.

Re: My Network Places

Nick Seng17-Aug-03 20:02

Nick Seng

17-Aug-03 20:02

Thanks. I'll take a look at that now.

God, I pity me! - Phoncible P. Bone

If I end up Windows ME someone is going to be hurting. - One of the answers to a question for What OS are you

Problem whit loops :x

heelios17-Aug-03 16:03

heelios

17-Aug-03 16:03

Hi,
Im having issues whit a loop.

When i try to return the function in the loop, it tells me the function has no return value.

		[WebMethod]<br />
		public string GetBiosInfo(string Username, string Password)<br />
		{<br />
			ConnectionOptions co = new ConnectionOptions();<br />
			co.Username = Username;<br />
			co.Password = Password;<br />
			ManagementScope ms = new System.Management.ManagementScope("\\\\127.0.0.1\\root\\cimv2", co);<br />
<br />
			ObjectQuery oq = new ObjectQuery("SELECT * FROM Win32_BIOS WHERE PrimaryBIOS = TRUE"); <br />
			ManagementObjectSearcher query = new ManagementObjectSearcher(ms,oq);<br />
			ManagementObjectCollection queryCollection = query.Get();<br />
<br />
			foreach(ManagementObject mo in queryCollection) <br />
			{<br />
				return mo["Name"].ToString();<br />
			}<br />
		}

Nathan Blomquist17-Aug-03 17:02

Nathan Blomquist

17-Aug-03 17:02

What the compiler is saying, is that "not all code paths return a value". This is because you don't return anything outside the foreach loop.

The problem lies in the fact that it is theoritically possible that the queryCollection is empty. If it is empty you bypass the loop and go directly to the end of the method. Return something after the loop and the problem will go away.

Also, are you sure you only want to execute the loop once? I mean right when you enter the foreach for the first time you will be exiting the method also.

-Nathan

---------------------------
Hmmm... what's a signature?

datagrid update failure

dorianr17-Aug-03 14:36

dorianr

17-Aug-03 14:36

I have a C# windows appliation with an Access database. There are 2 tables: USERS and PERMISSION_TYPES. Table definitions are:

Table Name: USERS
Fields:
First_Name
Last_Name
Address
PERMISSION_TYPE (FK to PERMISSION_TYPES)

Table Name: PERMISSION_TYPES
Fields:
PERMISSTION_TYPE (PK)
DESCRIPTION

The tables are linked vis the PERMISSION_TYPE field. I can make successful updates to the database, however, I'm trying to use a datagrid for each table so the user can Insert, Update, and Delete records in each table.

When the PERMISSION_TYPES.DESCRIPTION field is changed, an error message is returned that states:

"The record cannot be deleted or changed because table 'USERS' includes releated records"

This doesn't make any sense to me, since the DESCRIPTION field is not a Primary Key, and the updates are successful within Access. I have used the generated Update code, and I have written my own update code - I get the same error message.

Does anyone know what is wrong? Frown | :(

Thanks so much,
Randy
dorianr@mail.com

Sascha Andres17-Aug-03 23:37

Sascha Andres

17-Aug-03 23:37

Hi Randy,
dorianr wrote:
This doesn't make any sense to me, since the DESCRIPTION field is not a Primary Key, and the updates are successful within Access. I have used the generated Update code, and I have written my own update code - I get the same error message.
This sounds really a bit strange - just as the line would first be deleted, and later inserted again Confused | :confused:

I think PERMISSION_TYPES is just a lookup table. Something that helps
the user of your program to sort the records in the user table. Personally I prefer not to have the user edit a lookup table side by side of the main table.

I do this because:

the permission type is linked to more than one line, editing with only one row is usually specific, and lookups should be general
On a multi user system not all users should have adminstrator priviledges, eg access to the options. Defining possible permissiontypes (or more general: options)is the admins task

OK, this does not really solve your problem with the table, but perhaps an other way of doing things might be helpful.

Sascha

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

dorianr18-Aug-03 18:42

dorianr

18-Aug-03 18:42

Hi Sascha,

I'm wondering if there is a problem with the datagrid in .NET 2003 (I have experienced other bugs, but that is anther story). The two tables that I'm discussing are both lookup table that are in the Administration module (not all users have access).

I can solve this problem by adding a numeric, primary key to the PERMISSIONS_TYPE lookup table. I have no idea why using a PK for PERMISSION_TYPE would not let an Administrator update the permission type DESCRIPTION. This solution isn't very feasible, since I'm on the last part of a large project - it would set us back by a lot.

Thanks,
Randy

Ista18-Aug-03 17:02

Ista

18-Aug-03 17:02

that and your violating a relationship issues.

I.E.. see FOREIGN KEY RELATIONSHIPS in dbase theory

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

dorianr18-Aug-03 18:45

dorianr

18-Aug-03 18:45

I'm not violating FOREIGN KEY RELATIONSHIPS, since I can perform this update directly in the relational database. The problem seems to be with using .NET 2003. I've run tests, and I can perform the same update within the database, just not via .NET