C# Programming - Classes and Objects - Discussion

0 0 are default values set by constructor when object gets created.

Assignment should done to the different variables.

That's why it is printing default var 0 0?

class Sample
{
int i;
Single j;
public void SetData(int i, Single j)
{
i = i;
j = j;
}
public void Display()
{
Console.WriteLine(i + " " + j);
}
}

In the above code we are using local variables with same name as instance variable, because local variable will hide the instance variable. Instance variables will not get initialize. To refer the instance variable in case of local variable name is same as instance variable, use this keyword.

like this.i = i; //here this.i refer to instance variable i.

Here in the above:

public void SetData(int i, Single j)
{
i = i;
j = j;
}

We are trying to assign the value to the local variable that is,
i=i;
j=j;
So to resolve this problem we should write like :

public void SetData(int i, Single j)
{
this.i = i;
this.j = j;
}

This is an object of current class ,when the function call like:
sample obj1=new sample();

Then 'this' object contains the address of obj1 and now this directly referred to the object to obj1 and now it will store the value into the data field of object.

It is because the s1.SetData(10, 5.4f); will set the values if i, j but in line s1.Display(); function will call default constructor and default values assigned to i,j (0,0) . that is why it will print 0 0

The code is write is perfect but the on the time of value initialization it's initializing himself rather than to the variable declares in the class. Have a look in the below snippet.

class Sample
{
int i;
Single j;
public void SetData(int i, Single j)
{
this.i = i;
this.j = j;
}
public void Display()
{
Console.WriteLine(i + " " + j);
}
}

Here don't use this keyword that's why does not takes values for example if u take this.i and this.j in setdata then u will print some values so output is 0 0.

Actually it works just like the "ref" and "out" type variables, when you type :

this.varialblename

The variable references to the variable in the constructor.

If you run this program using "this" keyword the answer becomes 10 and 5.4 and them how come zero?

Instance variable name and local variable name of method is same, that's why local variable hide the instance variable, if you want to run this, you should be use "this" keyword as like :

public void SetData(int i, Single j)
{
this.i = i;
this.j = j;
}

If you run without "this" then result remains as zero only.