C # inheritance

For example:
There is a base class rectangleex 1 Class Rectangleex
2 {
3 Private   Int _ X, _ y, _ w, _ H;
4
5 Public   Int X
6 {
7 Get { Return _ X ;}
8 Set {_ X = Value ;}
9 }
10 Public   Int Y
11 {
12 Get { Return _ Y ;}
13 Set {_ Y = Value ;}
14 }
15 Public   Int W
16 {
17 Get { Return _ W ;}
18 Set {_ W = Value ;}
19 }
20 Public   Int H { Get { Return _ H ;} Set {_ H = Value ;}}
21
22 Protected Pen _ pen;
23
24 Public Rectangleex ( Int X, Int Y, Int W, Int H)
25 {
26 _ X = X;
27 _ Y = Y;
28 _ W = W;
29 _ H = H;
30 _ Pen =   New Pen (color. Black );
31 }
32
33 //
34 Public   Virtual   Void Draw (Graphics g)
35 {
36 G. drawrectangle (_ pen, _ x, _ y, _ w, _ H );
37 }
38
39 }

You can use: 1
2 Graphics g = E. graphics;
3 Pen P =   New Pen (color. Blue );
6
7 // Use rectangleex class instance;
8 Rectangleex Rex =   New Rectangleex ( 15 , 15 , 30 , 30 );
9 Rex. Draw (g );
10 .

Now you need to draw a square, which can be like this: 1 Class Square: rectangleex
2 {
3 Public Square ( Int X, Int Y, Int W)
4 : Base (X, y, W, W)
5 {
6 }
7 }

The above base is the same usage as the initialization list of c ++. when calling the base class method in C #, you can use the base keyword

Usage: 1
2 // Use Square
3 Square SQ =   New Square ( 20 , 20 , 20 );
4 Sq. Draw (g ); // The above griphics object from painteventargs e is used.
5

In this case, if I want to have a new derived class and draw two rectangles at the same time, I need to transform the draw () method (I have two methods)
First: I can change the draw () method of the base class to virtual, and then the derived class override it;
Second: I can also use the new keyword to hide methods with the same name in the base class.
The second method is as follows: 1 Class Dblrectangleex: rectangleex
2 {
3 Public Dblrectangleex ( Int X, Int Y, Int W, Int H ): Base (X, y, W, h ){
4 _ Pen =   New Pen (color. Red );
5
6 }
7
8 Private Pen _ rpen =   New Pen (color. seagreen );
9
10
11 Public   New   Void Draw (Graphics g) // Use the New Keyword to overwrite the method of the same name in the base class.
12 {
13 G. drawrectangle (_ pen, X, Y, W, H );
14 G. drawrectangle (_ rpen, X + 5 , Y + 5 , W, H );
15 }
16
17 /*
18 Public override void draw (Graphics g) // if the method is the same (parameters and return values), only override can be used (Virtual keywords are required for base class Declaration)
19 {
20 G. drawrectangle (_ pen, X, Y, W, H );
21 G. drawrectangle (_ rpen, x + 5, Y + 5, W, H );
22 } */
23
24
25 }