C# is language which operates with two kind of types:

• value type - type where only one space of memory is allocated. It is related for primitive C# types like: int, char, float, bool etc. as well as for struct types. If you copy value type to another type new instance of object will be created.
• reference type - type related to class objects. When we are declaring such class object, two memory spaces are being allocated. Object of class type and reference for such object. If you copy reference type to another reference type, only reference is being coping. It means that both references will be able to operate (ex. modify) the same object. Threfore when we modify object using one reference and will try to get its fields values using second reference, fields will have values after modification. As opposed to C++, there is possible to create reference type being not related to any object - null reference. Reference types in C# are very similar to pointers in C++.

Let's see example before for better understanding: Output of this example is: In point I we are declaring class TestClass which will be base for our reference type object.

In point II we are declaring struct TestStruct which is base for our value type object.

Point III presents initialization and assigning basic values for three different objects:

• class type object being reference type object
• struct type object being value type object
• primitive type (int type) object being value type object

and displaying value of our objects in point IV. Point V is key point of this example. Here we are passing our objects to the function and trying to modify its values there in order to check difference between reference type and value type.

Point VI prints values of our objects after invoking changeValuesOfClassAndStruct() function.

As you can see value of class type is being changed, while values of struct types and int type are not being changed. It is because default parameters passing to the function in C# is passing by value. This means we are copying object which we are passing to the function and copy of such object is being visible only within function.

However when we are passing reference type object we are passing reference to our object by value (copying reference to object - creating second reference to object), which allows as to see modified objects after exiting function using first reference to the object. So second copy of our reference is visible only withing function, but thanks to first copy of reference to the same object which is visible outside the function we can see modified object outside of function.

Reference and value types are one of major basic concepts which every C# developer should understand. This concept sometimes confuses people switching to C# from C++ programming language, where reference to object always have is marked using '&' character. In C# it is not required - instead we need to remember that every class type is reference type.

Code of above example can be downloaded from this blog's GitHub repository. You can find it here: Value and reference types

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In order to call one constructor from another constructor in C# programming language you can use below syntax:

class Plane

{

 Plane (){}

 Plane (int a) : this() {}

 Plane (int a, int b) : this(int a) {}

}

In above example constructor Plane (int a) invokes parameterless constructor Plane(). Constructor Plane(int a, int b) invoke two above constructors nested.

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