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.

Continue reading

Exploring Nullable types : Part 1

In this post, I am going to talk about Nullable types. Actually most of developers know, in c# we have
mainly two types.
– Reference type
– Value type.
But we have more type, that is called Nullable type.

Actually it is a value type but it has feature of both reference and Value type.

Continue reading

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…

Cheers,

Bri

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!!

Brij

String.IsNullOrEmpty

Might be some of you already using this. But for others it could be a great utility method.

We use a method static method IsNullOrEmpty of string in most of our daily task/Projects a lot. It works fine in most of the cases, but it could work bizarre in some cases if not handled properly.

Say, you get a entry from UI, and having a check whether user has entered something or not. It would work fine as long as user enters the data or not.

But what happen if user enters just spaces. This method would return false, ironically this method is behaving as coded. But do we need this?

Obviously not, spaces could lead wrong entry in our database even can corrupt the data and leads to uncommon results/Y SODS/malfunctioning.

Although being a good developer, one always trim the input before having the check. But it also tends a lots of extra LOCs which we can save and can make our system less error prone.

As most of aware that the beauty of the extension methods that were introduced in c#3.0. So we can have a extension method over a string, which actually does the both first trimming and then checking for IsNullOrEmpty.

So we can have the extension method as

public static bool IsNullorEmpty(this String val)
 {
 if (val != null)
 {
 if (string.IsNullOrEmpty(val.Trim()))
 return true;
 else
 return false;
 }
 return true;
 }

Lets see both existing and our new method running.

My code is

static void Main(string[] args)
 {
 string name = "   ";
 Console.WriteLine(String.IsNullOrEmpty(name));
 Console.WriteLine(name.IsNullorEmpty());
 Console.ReadKey();
 }

The output is

Output

But if you are still using .NET 2.0, you can have a normal static method in your utility call, which does the job for as.

public static bool CheckNullorEmpty(string val)
 {
 if (val != null)
 {
 if (string.IsNullOrEmpty(val.Trim()))
 return true;
 else
 return false;
 }
 return true;
 }

Note: I must say, the limitation of existing IsNullorEmpty has been resolved in .NET 4.0. Means you don’t need to do all this. There is a new method String.IsNullOrWhiteSpace will do the both for you. But unlikely, most of us still working on .NET2.0/3.5

Hope you all must have liked it.

Exploring Action Delegate

We used delegate a lot in some or other way. Like as we know, the event base model that we use in windows as web programming, is based on delegate only. I am in the habit of using delegates often. In last few days, I found a very elegent way to use the delegate.I was in the habit of of using only generic delegates that allows us type safety and lot more flexibility.

In our traditional programming, we use the delegate as in the following steps.

  1. Declaring the delegate
  2. Creating object of the delegate and assigning it to appropriate function
  3. Calling the delegate

Lets see the code

 public class Program
    {
        //Declaring an delegate
        public delegate void MyDelegate<R, S>(R r, S s);
        public static void Main(string[] args)
        {
            //Creating an Action variable and assigning it to a function
            MyDelegate<int, int> m1 = Multiply;
            //Calling the method
            m1(3, 4);
            Console.ReadKey();
        }

        public static void Multiply(int i, int j)
        {
            Console.WriteLine(i * j);
        }
    }

.NET 2.0 introcuced one generic delegate Action which takes a single parameter and returns nothing. Its declaration is
Public delegate void Action<T1>(T1 t1) // Takes 1 parameter and returns nothing
This is a very much elegatent way to use the delegate.

And C# 3.0, introduced 4 delegates which are as

  1. Public delegate void Action() // Takes no parameter and returns nothing
  2. Public delegate void Action<T1,T2>(T1 t1,T2 t2) // Takes 2 parameters and returns nothing
  3. Public delegate void Action<T1,T2,T3>(T1 t1,T2 t2,T3 t3) // Takes 3 parameters and returns nothing
  4. Public delegate void Action<T1,T2,T3,T4>(T1 t1,T2 t2,T3 t3),T4 t4) // Takes 4 parameters and returns nothing

Lets see them running

public class Program
{
public static void Main(string[] args)
{
//Creating an Action variable and assigning it to a function
Action myAction = Multiply;
//Calling the method
myAction(3, 4);

//Also can be called as
myAction.Invoke(3, 4);
}

public static void Multiply(int i,int j)
{
Console.WriteLine(i * j);
}
}

As from the code, we can also see that Action delegate also provide a method invoke to call the method.

These Action delegate also can be used with Anonymous Methods as

public class Program
{
public static void Main(string[] args)
{
//Creating an Action variable and assigning it to a function
Action myAction = delegate(int i, int j) { Console.WriteLine(i * j); };
//Calling the method
myAction(3, 4);

Console.ReadKey();
}
}

Also can be used with lambda function. Lets see

public class Program
    {
        public static void Main(string[] args)
        {
            //Creating an Action variable and assigning it to a function
            Action<int> myAction = s => Console.WriteLine(s * 5);
            //Calling the method
            myAction(3);

            Console.ReadKey();
        }
    }

So code delegently and efficiently.

Note: The ForEach and ForEach<T> methods each take an Action<T> delegate as a parameter. The method encapsulated by the delegate allows us to perform an action on each element in the array or list.

Happy .Neting….

Cheers,
Brij