What is .NET Remoting?

.NET Remoting is an enabler for application communication. It is a generic system for different applications to use to communicate with one another. .NET objects are exposed to remote processes, thus allowing interprocess communication. The applications can be located on the same computer, different computers on the same network, or even computers across separate networks.

.NET Remoting versus Distributed COM

In the past interprocess communication between applications was handled through Distributed COM, or DCOM. DCOM works well and the performance is adequate when applications exist on computers of similar type on the same network. However, DCOM has its drawbacks in the Internet connected world. DCOM relies on a proprietary binary protocol that not all object models support, which hinders interoperability across platforms. In addition, have you tried to get DCOM to work through a firewall? DCOM wants to communicate over a range of ports that are typically blocked by firewalls. There are a ways to get it to work, but they either decrease the effectiveness of the firewall (why bother to even have the firewall if you open up a ton of ports on it), or require you to get a firewall that allows support for binary traffic over port 80.
.NET Remoting eliminates the difficulties of DCOM by supporting different transport protocol formats and communication protocols. This allows .NET Remoting to be adaptable to the network environment in which it is being used.

.NET Remoting versus Web Services

Unless you have been living in a cave, or are way behind in your reading, you have probably read something about Web services. When you read the description of .NET Remoting it may remind you a lot of what you're read about Web services. That is because Web services fall under the umbrella of .NET Remoting, but have a simplified programming model and are intended for a wide target audience.
Web services involve allowing applications to exchange messages in a way that is platform, object model, and programming language independent. Web services are stateless and know nothing about the client that is making the request. The clients communicate by transferring messages back and forth in a specific format known as the Simple Object Access Protocol, or SOAP. (Want to get some funny looks in the hallway? Stand around in the hallway near the marketing department with your colleagues and discuss the benefits of using SOAP).

The following list outlines some of the major differences between .NET Remoting and Web services that will help you to decide when to use one or the other:

· ASP.NET based Web services can only be accessed over HTTP. .NET Remoting can be used across any protocol.

· Web services work in a stateless environment where each request results in a new object created to service the request. .NET Remoting supports state management options and can correlate multiple calls from the same client and support callbacks.

· Web services serialize objects through XML contained in the SOAP messages and can thus only handle items that can be fully expressed in XML. .NET Remoting relies on the existence of the common language runtime assemblies that contain information about data types. This limits the information that must be passed about an object and allows objects to be passed by value or by reference.

· Web services support interoperability across platforms and are good for heterogeneous environments. .NET Remoting requires the clients be built using .NET, or another framework that supports .NET Remoting, which means a homogeneous environment.

Overview

1. Current component technologies do not inter-operate. While they all dealt with components and objects, they differed over lifecycle management, constructor details, degree of support for inheritance and so on.
2. Current component technologies focus on RPC-style communication. This led to tightly coupled systems built around the invocation of object methods.

Serialization & Metadata

• Marshal instances of programmatic data types into messages that can be sent across the network via data packets. This is usually accomplished via some serialization of marshalling engine.
• Provide a description of what those messages look like. This is usually accomplished through some form of metadata. In the case of COM/DCOM, the serialization engine was the Type Library Marshaler, and the metadata was provided by the type library.

ASP.NET Web Services: XmlSerializer and XSD

.NET Remoting: IFormatter and the CLR.

.NET Remoting and ASP.NET Web Services

Distributed Application Design

Transport Protocols & Host Processes

Technology	Transport Protocols	Host Processes
ASP.NET Web Services	HTTP only	IIS only (aspnet_wp.exe)
.NET Remoting	HTTP and TCP	IIS, Windows Forms, Windows Services, and console apps.

Security

Technology	Security
ASP.NET Web Services	Uses the security features of IIS by default
.NET Remoting	Cross-process calls are not secured. Will use the security features of IIS only if deployed in IIS.

State Management

Technology	State Management
ASP.NET Web Services	Stateless by default. State can be managed using standard ASP.NET objects or a custom solution
.NET Remoting	Different management options depending on the type of the remote object.

Performance

Choosing an Architecture

• By default, use ASP.NET Web Services. They are simpler to implement and use, and offer the broadest reach to clients.
• Consider .NET Remoting if you need a more traditional distributed object model with full CLR type fidelity, don't need interoperability with other platforms, and have control over client and server configurations.
• If you choose .NET Remoting, prefer the HTTP channel registered with IIS and ASP.NET. Otherwise, you will have to build your own process lifecycle management and security infrastructure.
• Given that .NET Remoting requires .NET client, it makes sense to use the binary formatter instead.
• Use Enterprise Services when you need declarative transactions.

Tell me something about yourself.

This is the vital question of the interview. Before answering this question you must understand the purpose behind it. The answer to this question reflects what you think about yourself.

The answer should be in such a way that it should not be like you are reading your CV all over again. It can be something like -
Sir , as you already know my name is XXXXx. Tell about your birth place, schooling details…..till college. Discuss the time from your birth till now…….There is no need to mention the percentage of marks you scored in the school. You can mention the percentage of marks you scored in college, if it is good.

In the end finish it with a question, for e.g., Is there any thing else you would like to know about me, sir?

Tell me something about your parents.

My father’s name is XXXXXX. Discuss his occupation along with his contribution to society and role played by him in society.

About your mother same as above if she is working.

If she is a house wife then never undermine her contribution by referring to her as a simple house wife. You should portray her as a house maker. Along with this, mention that she is doing her job since so many years consistently without any leave and any appreciation.

If you want to change any thing in your life, what will you change?

I am very much happy and satisfied with my life, this is the gift of god. But then also, if ever in life knowingly or unknowingly I have ever hurt my elders (parents, teachers), I just want to change that like it never happened and say sorry to them.

What is your weakness or what are you afraid of?

Most appropriate answer would be something like – Sir, I can make a presentation in front of hundreds of people but whenever it came to sing a song in the class, I really shivered and I couldn’t sing even a single line. Your weakness should be presented in such a manner that it doesn’t seem to be your weakness.

What package you are looking for?

For freshers:
You are very lucky that you are sitting in an interview……you can’t be demanding. Your answer should be, sir as per company policy whatever package would be offered I’ll accept that. But this is a very casual answer.
Your answer should be something like: “Sir, as you know I am a fresher and the only thing I can expect at this point of time is that I should get a job in a prestigious company like yours. Of course every one works for money I would be expecting something which is sufficient to make my living in a city and I should be able to support my family a bit.

Do you have a girl friend/Wife?

Always speak the truth in your interview, never tell lies. Your views about her should not be orthodox and you should always be supporting and encouraging towards her.

What is your Vision?

The answer for this question is to be decided by you. Before you start answering, you should understand the meaning of “vision”. Vision is a long term task/goal or long life commitment. Now this commitment can be with yourself, towards your society, wife, parents etc. e.g. I want to open an orphanage after finishing all family responsibilities.

What is the mission of your life?

This is same as vision but the only difference is that mission is for short terms. Like when you were in class XII your mission was to get admission in a good Engineering College. It keeps changing with time.

Where do you see yourself after 2-3 years from now?

The answer for this question varies from company to company and it depends on the hierarchy of the company. Your answer should be something like: Sir, initially I would be learning and knowing my work and company. In a year or after 1 year I expect from myself to be an expert in solving the issues on L1 level. And after that I would like to get a certification on the technology I am working. So within 2-3 yrs I expect myself to be a proficient engineer on L2 level.

What are your hobbies?

This is a very tricky question, I repeat very tricky question. You should mention your hobbies in which you have deep knowledge. Like cricket or playing cricket, by mentioning cricket you have given a wide scope to the interviewer as he can ask any thing from cricket infact he can ask any year also. But by mentioning playing cricket you have reduced the scope. Another e.g. is Music and Listening Music. Mentioning reading as your hobby is very risky because if you have read some books and the interviewer has also read it then he can ask a lot of questions related to it. You should be very cautious about it.

What kind of a person are you - Introvert/Extrovert?

Being totally introvert or extrovert is not right. You should be having a mixed behavior and behave as per the requirement of the situation. You can say something like- Sir, I behave according to the place and situation. Eg. Introvert personally and extrovert professionally.

Do you believe in competition or team work?

According to famous phrase “necessity is the mother of invention”. If there is no competition then there will not be any growth, the growth can be professional or personal. For any project or any work, team work is most important because a single person cannot do anything alone.

Competition and team work both are important.

If your manger has given you a task and your manager’s manger is saying not to do that work, what you will do? You will obey your manager or his manager?

I will obey my manager, as I believe that if my manager has assigned me a work he must have discussed it with his manager. I am his resource and my role is to obey him.

In a catastrophic situation like fire what you will do?

No heroic an answer is expected from you. They want to see how you would behave in such a situation. You can say something like – First, I would ensure my safety and then I will inform the fire department of company and city. If I am in a position of helping someone then I would definitely do that.

If you get a better package than here what will you do accept that offer or reject that?

This question means a lot. HR people want that the hired person should serve the company for longer period. You can say something like: Sir, as you know I am a fresher and if I switch the jobs very quickly then it will be a question mark on my stability, which will affect my career. Above all, I have to learn and increase my technical knowledge as well. Money comes with knowledge. So, I am here to learn and provide my best to the company.

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INTRODUCTION

TRIGGERS IN SQL SERVER

BACKGROUND

This article gives a brief introduction about Triggers in Sql Server 2000/2005.

What is a Trigger

A trigger is a special kind of a store procedure that executes in response to certain action on the table like insertion, deletion or updation of data. It is a database object which is bound to a table and is executed automatically. You can’t explicitly invoke triggers. The only way to do this is by performing the required action no the table that they are assigned to.

Types Of Triggers

There are three action query types that you use in SQL which are INSERT, UPDATE and DELETE. So, there are three types of triggers and hybrids that come from mixing and matching the events and timings that fire them.

Basically, triggers are classified into two main types:-

(i) After Triggers (For Triggers)
(ii) Instead Of Triggers

(i) After Triggers

These triggers run after an insert, update or delete on a table. They are not supported for views.
AFTER TRIGGERS can be classified further into three types as:

(a) AFTER INSERT Trigger.
(b) AFTER UPDATE Trigger.
(c) AFTER DELETE Trigger.

Let’s create After triggers. First of all, let’s create a table and insert some sample data. Then, on this table, I will be attaching several triggers.

CREATE TABLE Employee_Test
(
Emp_ID INT Identity,
Emp_name Varchar(100),
Emp_Sal Decimal (10,2)
)

INSERT INTO Employee_Test VALUES ('Anees',1000);
INSERT INTO Employee_Test VALUES ('Rick',1200);
INSERT INTO Employee_Test VALUES ('John',1100);
INSERT INTO Employee_Test VALUES ('Stephen',1300);
INSERT INTO Employee_Test VALUES ('Maria',1400);

I will be creating an AFTER INSERT TRIGGER which will insert the rows inserted into the table into another audit table. The main purpose of this audit table is to record the changes in the main table. This can be thought of as a generic audit trigger.

Now, create the audit table as:-

CREATE TABLE Employee_Test_Audit
(
Emp_ID int,
Emp_name varchar(100),
Emp_Sal decimal (10,2),
Audit_Action varchar(100),
Audit_Timestamp datetime
)

(a) AFTRE INSERT Trigger

This trigger is fired after an INSERT on the table. Let’s create the trigger as:-

CREATE TRIGGER trgAfterInsert ON [dbo].[Employee_Test] 
FOR INSERT
AS
 declare @empid int;
 declare @empname varchar(100);
 declare @empsal decimal(10,2);
 declare @audit_action varchar(100);

 select @empid=i.Emp_ID from inserted i; 
 select @empname=i.Emp_Name from inserted i; 
 select @empsal=i.Emp_Sal from inserted i; 
 set @audit_action='Inserted Record -- After Insert Trigger.';

 insert into Employee_Test_Audit
           (Emp_ID,Emp_Name,Emp_Sal,Audit_Action,Audit_Timestamp) 
 values(@empid,@empname,@empsal,@audit_action,getdate());

 PRINT 'AFTER INSERT trigger fired.'
GO

The CREATE TRIGGER statement is used to create the trigger. THE ON clause specifies the table name on which the trigger is to be attached. The FOR INSERT specifies that this is an AFTER INSERT trigger. In place of FOR INSERT, AFTER INSERT can be used. Both of them mean the same.
In the trigger body, table named inserted has been used. This table is a logical table and contains the row that has been inserted. I have selected the fields from the logical inserted table from the row that has been inserted into different variables, and finally inserted those values into the Audit table.
To see the newly created trigger in action, lets insert a row into the main table as :

insert into Employee_Test values('Chris',1500);

Now, a record has been inserted into the Employee_Test table. The AFTER INSERT trigger attached to this table has inserted the record into the Employee_Test_Audit as:-

6   Chris  1500.00   Inserted Record -- After Insert Trigger. 2008-04-26 12:00:55.700

(b) AFTER UPDATE Trigger

This trigger is fired after an update on the table. Let’s create the trigger as:-

CREATE TRIGGER trgAfterUpdate ON [dbo].[Employee_Test] 
FOR UPDATE
AS
 declare @empid int;
 declare @empname varchar(100);
 declare @empsal decimal(10,2);
 declare @audit_action varchar(100);

 select @empid=i.Emp_ID from inserted i; 
 select @empname=i.Emp_Name from inserted i; 
 select @empsal=i.Emp_Sal from inserted i; 
 
 if update(Emp_Name)
  set @audit_action='Updated Record -- After Update Trigger.';
 if update(Emp_Sal)
  set @audit_action='Updated Record -- After Update Trigger.';

 insert into Employee_Test_Audit(Emp_ID,Emp_Name,Emp_Sal,Audit_Action,Audit_Timestamp) 
 values(@empid,@empname,@empsal,@audit_action,getdate());

 PRINT 'AFTER UPDATE Trigger fired.'
GO

The AFTER UPDATE Trigger is created in which the updated record is inserted into the audit table. There is no logical table updated like the logical table inserted. We can obtain the updated value of a field from the update(column_name) function. In our trigger, we have used, if update(Emp_Name) to check if the column Emp_Name has been updated. We have similarly checked the column Emp_Sal for an update.
Let’s update a record column and see what happens.

update Employee_Test set Emp_Sal=1550 where Emp_ID=6

This inserts the row into the audit table as:-

6  Chris  1550.00  Updated Record -- After Update Trigger.   2008-04-26 12:38:11.843 

(c) AFTER DELETE Trigger

This trigger is fired after a delete on the table. Let’s create the trigger as:-

CREATE TRIGGER trgAfterDelete ON [dbo].[Employee_Test] 
AFTER DELETE
AS
 declare @empid int;
 declare @empname varchar(100);
 declare @empsal decimal(10,2);
 declare @audit_action varchar(100);

 select @empid=d.Emp_ID from deleted d; 
 select @empname=d.Emp_Name from deleted d; 
 select @empsal=d.Emp_Sal from deleted d; 
 set @audit_action='Deleted -- After Delete Trigger.';

 insert into Employee_Test_Audit
(Emp_ID,Emp_Name,Emp_Sal,Audit_Action,Audit_Timestamp) 
 values(@empid,@empname,@empsal,@audit_action,getdate());

 PRINT 'AFTER DELETE TRIGGER fired.'
GO

In this trigger, the deleted record’s data is picked from the logical deleted table and inserted into the audit table.
Let’s fire a delete on the main table.
A record has been inserted into the audit table as:-

6  Chris 1550.00  Deleted -- After Delete Trigger.  2008-04-26 12:52:13.867 

All the triggers can be enabled/disabled on the table using the statement

ALTER TABLE Employee_Test {ENABLE|DISBALE} TRIGGER ALL 

Specific Triggers can be enabled or disabled as :-

ALTER TABLE Employee_Test DISABLE TRIGGER trgAfterDelete

This disables the After Delete Trigger named trgAfterDelete on the specified table.

(ii) Instead Of Triggers

These can be used as an interceptor for anything that anyonr tried to do on our table or view. If you define an Instead Of trigger on a table for the Delete operation, they try to delete rows, and they will not actually get deleted (unless you issue another delete instruction from within the trigger)
INSTEAD OF TRIGGERS can be classified further into three types as:-

(a) INSTEAD OF INSERT Trigger.
(b) INSTEAD OF UPDATE Trigger.
(c) INSTEAD OF DELETE Trigger.

(a) Let’s create an Instead Of Delete Trigger as:-

CREATE TRIGGER trgInsteadOfDelete ON [dbo].[Employee_Test] 
INSTEAD OF DELETE
AS
 declare @emp_id int;
 declare @emp_name varchar(100);
 declare @emp_sal int;
 
 select @emp_id=d.Emp_ID from deleted d;
 select @emp_name=d.Emp_Name from deleted d;
 select @emp_sal=d.Emp_Sal from deleted d;

 BEGIN
  if(@emp_sal>1200)
  begin
   RAISERROR('Cannot delete where salary > 1200',16,1);
   ROLLBACK;
  end
  else
  begin
   delete from Employee_Test where Emp_ID=@emp_id;
   COMMIT;
   insert into Employee_Test_Audit(Emp_ID,Emp_Name,Emp_Sal,Audit_Action,Audit_Timestamp)
   values(@emp_id,@emp_name,@emp_sal,'Deleted -- Instead Of Delete Trigger.',getdate());
   PRINT 'Record Deleted -- Instead Of Delete Trigger.'
  end
 END
GO

This trigger will prevent the deletion of records from the table where Emp_Sal > 1200. If such a record is deleted, the Instead Of Trigger will rollback the transaction, otherwise the transaction will be committed.
Now, let’s try to delete a record with the Emp_Sal >1200 as:-

delete from Employee_Test where Emp_ID=4

This will print an error message as defined in the RAISE ERROR statement as:-

Server: Msg 50000, Level 16, State 1, Procedure trgInsteadOfDelete, Line 15
Cannot delete where salary > 1200 

And this record will not be deleted.
In a similar way, you can code Instead of Insert and Instead Of Update triggers on your tables.

CONCLUSION

In this article, I took a brief introduction of triggers, explained the various kinds of triggers – After Triggers and Instead Of Triggers along with their variants and explained how each of them works. I hope you will get a clear understanding about the Triggers in Sql Server and their usage.