Struct is value type defined in .Net and is actually mutable (means if I change member variable of struct it really get changed and do not
create new copy). Same thing is not true about String.
for ex, String str = "Hello";
str = str + "John";
The above operation would create new copy of string str and store in it "Hello John". Hence strings are immutable.
In case of struct,
struct rectangle
{
private int length;
public int Length
{
get
{
return length;
}
set
{
length = value;
}
}
private int width;
public int Width
{
get
{
return width;
}
set
{
width = value;
}
}
public void display()
{
Console.WriteLine("Length= {0} Width = {1}",length,width);
}
}
public static void Main()
{
rectangle r = new rectangle();
r.Length = 10;
r.Width = 20;
r.display();
//Length= 10 Width = 20
r.Length = 400;
r.display();
//Length= 400 Width = 20
//Here actual struct variable (r) is modified and displayed.
List
Room.Add(new rectangle { Length = 5, Width = 10 });
foreach (rectangle item in Room)
{
item.display();
}
//Length= 5 Width = 10
//Room[0].Length = 20; //error
Room[0] = new rectangle { Length = 20, Width = Room[0].Width };
foreach (rectangle item in Room)
{
item.display();
}
//Length= 20 Width = 10
rectangle[] walls = new rectangle[2];
walls[0] = new rectangle { Length = 10, Width = 30 };
walls[0].display();
//Length= 10 Width = 30
walls[0].Length = 40;
walls[0].display();
//Length= 40 Width = 30
}
So, if a struct is part of collection class (List
properties of struct variable, we have to use workaround as shown below
//Room[0].Length = 20; //error
Room[0] = new rectangle { Length = 20, Width = Room[0].Width }; // work around
In case of struct part of Array[], we can modify properties of struct as normal variable.
So this is the case where actual struct variable can not modified.
