04/02 Placing Controls In a Windows Form :

Date 4/2/11 Friday

- Add a new form in a project:

- IF we want one more form in the project we can add it from the add new item window, choosing the item template Windows Form. Once a new form is added to run the form we need to specify the form class name, under Application.Run method with in the class program.

EG:  Application.Run(new Form2());

- Binding an event procedure with multiple events of a control under VS.

- In the new form asses --> goto properties of it and double click on load event, which defines an event procedure Form2_Load --> Now again Goto events of form select Click event and choose Form2_Load event procedure under it.

- Now write the following code under event procedure, which gets executed for both Load and Click events.

Eg:  MessageBox.Show(“Bound with multiple events of a control”)

- Now add a new form, Form3 in project.

- Placing controls on a form:-

-        We have provided with number of controls for developing our application, where each control is define as a class.

-        These controls are avilabel under the tool box window arranged as groups (tabs).

-        To place a control of the form either choose your control and double click on it or select a control and place on the form so that the control is placed at that location. 

Note – use the layout tool bar for aligning of the controls.

- In form Form3 under project place three buttons on it.

- Goto events of button one double click on click event, which defines button1_Click event procedure, bind the event procedure with click event of button2, button3 and Form also.

- Then tried the following code under button1_Click event procedure.

if (sender.GetType().Name == "Button")             {              Button b = (Button)sender;                 if (b.Name=="button1")                     MessageBox.Show("Button1 is clisked");                 else if (b.Name=="button2")                     MessageBox.Show("Button2 is clisked");                 else if (b.Name=="button3")                     MessageBox.Show("Button3 is clisked");             }             else                 MessageBox.Show("Form is clicked");

Note - Goto the notes of inheritance , read the 2,3 and 4 rule , you can understand clearly , what we are doing.

- When a event procedure is bound with multiple controls, the object of the control, which has raised the event is sent to event procedure in run time and that get captured under sender parameter of event procedure.

- As a sender is of type object it can hold instance (or object) of any control that has raised the event which is sent to the event procedure in run time as following:

- in the above case we have bound the event procedure with diff type of controls (button and form) so first to identify the type of control it was used the get type method of object class and recognize the type of control (button or form), raised in the event.

- after recognizing the type of control it was if there are multiple controls of same type then we need to convert sender into the appropriate control type to identify the name of each control, because “sender” is of parent type it can not referred to members of it child class(button now).

- Converting sender into appropriate control type can be done in two ways as following:

Button b = (Button)sender; or Button b = sender as Button;