Working with EventViewer using C#

There are several phases of a Application . It does not end with developing the application and deploying it on production servers. Other most important part, any problem surfaces after the deployment, how quickly the problem can be be resolved and according to severity of the issue (if required) a patch can be deployed on production. Apart from this, we also want to get notified on all the issues occurred on production and accordingly analyze and take care in future releases. We can also log other details that could be useful to check the status of Application.

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Learning null-coalescing operator

I am pretty sure that most of the guys has never knew this operator and its also very rarely used. Since C# provides this and this is very useful and handy at certain times.

The short from of null-coalescing operator is ??.

It actually takes two operands.  So it returns the left hand operand if it is not null else returns right operand. So this is very useful while initializing any variable. let’s see a example

string name = null;
string otherName = "Brij";
string userName = name ?? otherName;

As you can see, here is name is null then userName is assigned to otherName. and it will print Brij.

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Exploring Nullable types : Part 2

This is second and last part of the post on Nullable type series. You can view the first part from here

Exploring Nullable types : Part 1

In this series, I will talking certain rules that we need to take care while using Nullable type. I will be taking scenario wise.

First scenario:

Int? a=8;
object o = a;
long d = (long)c;

It will be compiled successfully but will throw and Invalid Cast Exception. Means, you cannot cast it to any other type except the underlying type which is here int although  int type can be hold by long.

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Generics and Constraints over Generics

In this post,  I am going to discuss about Generic Classes and bit more on this.  Just for a smooth start,

“Generics were introduced in .NET 2.0, which provides us a way to create Classes/Methods/Types and many more without specifing the specific type of parameters. Parameters must be provided at the time of creating the instances. So we can say Generics are only a blueprint/templated version and actual type is defined at Runtime.”

So lets first create a simple Class say Point Continue reading…

Some basics about C#

I have seen a lot of confusion amongst a lot developers about some basic things of C#. I am going to discuss some of them here.

The very first thing, In C# every thing is a struct or a Class. And every type(Class) is a derived from System.Object, whether is of reference type or Value type.

All Value type variables are derived from System.Value type and System.Value type itself is derived from System.Object. And every value type variables is declared sealed type so no one can derive from it.

Now Lets move some basic Questions.

– What is the difference string, String and System.String?

– What is the difference amongst int, System.Int32, System.Int64.

So these are few basic things, some always have confusion. So lets try to clear it out.

int c;

System.Int32 c;

int c=0;

System.Int32 c = 0;

int c= new int();

System.Int32 c = new System.Int32();

So what is the difference in all above. or Is there any differences?

In one word answer: NO

All of the above would be compiled and will produce the same and exact IL code.

It means all of these are same. Actually C# define primitive types and every primitive is directly mapped to some Class in FCL. So whenever you are going to write the primitive type, compiler while compiling finds the exact Class from the FCL and replaces with it.

Similarly, System.String or String or string all are same. Even I had confusion earlier between String and string. Even when you type both in Visual Studio IDE, both are in different color.

One more thing, I want to say every value type is initialized to its defined default value. Whether you give its default value or not Compiler does it for you, but this is not true for Reference Type.

One already know, writing int is mapped Int32 or is of 32 bit. But some people have different view, according to them int is of 32 bit in 32 bit machines and is of 64 bit on 64 bit machines. Which is absolutely wrong and int is always of 32 bit in C#, whether is of 32 bit or 64 bit machines.

Hope it clears…



IS vs AS operators : Performance Implications

If you are working as a C# programmer. You must know, the differences and performance implications of these operators IS vs AS. Some people who has not enough information about this, it’ll be helpful to them.

There are two operators IS as AS in C# and mostly used for same purposes. During our programming, we generally typecast the object into other type.

There are various scenarios, if you are typecasting , you may compile time error and other Run time error. Which obviously is not good for any application.

One thing, first I want to discuss, that as we know, System.Object is mother of all classes in C#. It means, whether you derive your class from System.Object specifically or not, CLR does this for you. So every object has always few basic method, that are inherited from System.Object. GetType also comes from System.Object. This always gives you the exact type of your object at run time. This method is non virtual so yo are not allowed to override this.

Now lets move to Is operator. For the safety of the code, whenever you are going to cast an object to other, say Class Student . you will be writing the code like

if( myobject is Student )
 { Student objStudent = (Student) myobject;

Obviously this is good code, because before typecasting to Student type, it is actually checking whether this is of Student type or not. Is Operator returns true if the object is of the same type else return false.

But what happens, if we write the code simply

 Student objStudent = (Student) myobject;

and where myobject is not of Student type, it’ll throw an exception. Actually at run time, CLR checks whether the object is of student type or not and it is not, so it throws an exception.

Now lets move to AS operator, this operator try to to typecast the object to a given type and if the typecasting is successful then it returns it as of object of that class else returns null.

Now we can write the above code as following,

 Student objStudent =  myobject as Student;
 if(objStudent !=null)
 //use the object

Here as we see in the first line, CLR first checks whether the object is of Student type then return object of that type else null. Actually type checking is not a simple task for CLR, it goes through all the hierarchy, i e base type and checks whether the object is of the current type or any base type.

So in the second one, CLR is checking this once while earlier one it is doing two time, first with IS operator and later in typecasting, which is obviously a overhead.

Here I also want to mention one thing, we should use AS operator judiciously, because it will never throw an exception while typecasting, so one always must have a check for null, before using this else it’ll through an exception.

On the other hand, if you are assign any value , say a input box or Label, one should use as operator. We can do in two ways, say we got one data row that came from database. Now,

textbox1.Text = data row["columnName"] as String;

because Text property can be assign any string or null, it will never barf. So this will work every time, but if you write

textbox1.Text = data row["columnName"].ToString();

It will be working fine till the value is not null else will through an exception because ToString() cannot be called over null value.

Hope you all have enjoyed this.

Happy coding!!


Concurrent Collections with .NET4.0

Earlier we used Collections, they were never ThreadSafe. Generics introduced in .NET 2.0 are TypeSafe but not ThreadSafe.

Generics are Typesafe means whenever you are going to declare any generic type, you need to specify the type that is going to be held by the List. And whenever you are going to retrieve any item from list you will get the actual type item, not an Object like we get from Arraylist.

But Generics are not ThredSafe, it’s a programmer’s responsibility. Means let’s say if you have an list collecting some objects. That list is shared amongst several threads, the it may work hazardous if two threads try to access the List at the same point of time, like adding/removing/iterating  items from the same list at the same time.

Thread safety can be implemented with the help of locking the collection and other similar ways. But locking the entire list for the sake of adding/removing an item could be a big performance hit for an application based on the circumstances.

.NET 4.0 provides new classes for the concurrency as Concurrent collections. These are

  • ConcurrentDictionary< Key , Value> Thread safe dictionary in key value pairs.
  • ConcurrentQueue<T> Thread safe FIFO datastructure.
  • ConcurrentStact<T> Thread safe LIFO datastructure.
  • ConcurrentBag<T> Thread safe implementation of an unordered collection.
  • BlockingCollection<T> Provides a Classical Producer Consumer pattern.

Above all classes are available in the namespace System.Collections.Concurrent .

These collections allow us to share the data amongst several thread without any worry.

Concurrent Collections are the key of Parallel programming, that is introduced in .NET 4.0

So let’s discuss the very commonly used list ConcurrentDictionary

  • A thread safe add/remove from dictionary.
  • Very user friendly methods that make it unnecessary for code to check if a key exists before add/remove.
  • AddOrUpdate : Adds a new entry if doesn’t exist else updates existing one
  • GetOrAdd : Retrieves an item if exists, else first adds it then retrieve it
  • TryAdd, TrygetValue,TryUpdate, TryRemove : Allows to do the specified operation like Add/Get/Update/Remove and if it fails the does the alternative action.

Benefits of the above Concurrent collections:

  • Now programmer doesn’t need to take care on threadsafety.
  • Uses light weight synchronization like SpinWait, SpinLock etc that use spinning before putting threads to wait – for short wait periods, spinning is less expensive than wait which involves kernel transition.
  • Means faster add/remove/iterate in multithreading environment without writing the code for it.
  • Some other classes like ConcurrentQueue & ConcurrentStack don’t rely on Interlocked operations instead of locks which make them faster.

There is lot more to discuss on this. But keeping it short and simple, let’s finish it we’ll discuss other things coming subsequent posts.