.Net Remoting Activator Sample

download the Samaple Code

see the clip

In the previous lesson of Remoting I talked about remoting basics I examined a code sample. If you take a look to that post some people get back to me with the question how we can hide service from client process well this lesson is talk about how to hide Service from Client. First take a look to what we discussed in last lesson.

As you see in above diagram client application is talking to server application to create an object which will be created in server. This object metadata (definition) is inside service app. What client needs to talk to server application is a proxy object. This proxy object will be created based on one of the classes in service app. For example if you have a class called Test with one method called Dosth. The proxy object in client will be a class called Test with one method called Dosth. When this method is called proxy object path this call to the serve so in the server the real object will be created then the method in serve is called. So Server definitely needs the service app to understand the Type “Test”. The Issue here is that in reality in most of the projects we do not like to give client the service application because a clever client may open this library and then could be a threat to our business rule or security. But how client can create proxy object if no Type is available in client process?

See the movie please I explained more about this issue.

There are two ways to solve this issue:

1. You could create the same service app and change all code in new service app in a way that all methods even constructors throw an exception (I do not recommend this way since it is time consuming and there is no standardization. )


2. Using interface between client and server is another approach. It means that each class in service app inherits from an interface it means that we need extra application that has just interfaces. Client has this library from where it can find metadata to create the proxy object. Meanwhile, client is not able to see the service implementation. We are done, However, there is a big issue here: if we just give client an interface then the proxy object will be like interface how we are going to create an object from interface? Well we do not create proxy object. We use Activator class to create an object from server application but map that to the interface take a look to this picture
   

In above diagram as you see client just access to IService app that has just interface and interface does not have any implementation. And server has both of them. Server exposes Test object. Remember Test object is a type of ITest as well (because of inheritance) and client receive The test object but the way client look to Test object is ITest then when client call ITest methods the Test methods are called.

How to write activator code?
The coding that we had in previous example in client slightly changes take a look at this line of code. Let’s say I have a Hello class and IHello interface then the code in client is like this:

IHello h = (IHello)Activator.GetObject (typeof(IHello),"http://localhost:4000/Myuri");

Activator object create an object in server as you see and then map that type to interface. Please see the code and also the clip.

download the Samaple Code

see the clip

Multi tier Architecture utilities (NLOG)

see these Related topics:

1. Multi tier basics
2. A best practice for multi tier architecture
3. A sample code based on best practice
4. Examine utilities to speed up Multi tier programming- NLog

Please download the second version of Multi tier code

In previous lessons I talked about basic concepts of Multi tier and a best practice Architecture. Also I examine a sample code about that Architecture in this lesson I am going to review ”NLOG” one of the best tools that with no doubt you better use in that architecture to Log both errors and interaction with application.
What is NLOG?
NLOG is a free tool could be used to log into different resources like file, event viewer, database, Memory, Console, MSMQ, Mail and Web Service and etc. Meanwhile it can be configured to different level of log. Moreover, it can be switched off or on. Also you can have different source of log. Above of all it is open source application. Should you need any changes you will be able to make it.
How NLOG works?NLog gives you a class library to call its services. Also it has a configuration file called NLog.config where you set which log sources you need for instance file or database. Also you can configure the source for example for a file you probably configures the file name. You can have multiple sources. Take look at this sample:

this configuration file will be in UI application then other layers in Multi tier architecture do not need extra Nlog.config file all of them will use this configuration file. If you look at the logDirecotry in above code you will see that actually nlog will create a folder called Logs inside application folder and it will log data for each day. I just showed you logging in files. Log in other data sources like database has its own configuration variables.
It you look at the rules tag you will find two logger tags where you define each one of these logger
1- which class will represents them (“name”)
2- what is the minimum level of log also you can disable log by setting this value to debug for a release version of application (“minLevel”)
3- Which target this logger is using to log information

In a multi tier application we always put our logger in Common Layer because we need this library in other layers. Also I highly recommend you to write a rapper class to simplify using NLog. Take a look at the DataLogger code:

In above code simply two methods are written Info and Warn to log information. If you look at the parameters you see multiple parameters. To save these parameters an xml structure is being used.
Please see the next version of multi tier code with logging
I remind you that I used very simple logging here you may change it and adapt it to your requirements. So this is not a best practice however, it is a good practice using Nlog in your projects. Nlog is really a lot more than I show you here. If you need any extra information or you think it is worth to have more detail information about NLOG let me know and raise some comments here. Do not underestimate this fabulous tool. I believe it needs at least 20 posts to show its capability!
In next lesson I am going to talk about my favourite tool Code Smith to generate code. Please download the next version of the code.

Please download the second version of Multi tier code