Hello,Windows Forms

1. Hello,Windows Forms PRESENTED BY Minu Puranik And Vivekananthan Murugesan Summer 2002

2. Console V/S Windows Applications • Compiler switch names “target”. • For console we write /target:exe • For console we write /target:winexe • Console Application gets keyboard input through Console.Read Console.ReadLine • Windows Forms Applications gets keyboard(and other) input through “EVENTS”

3. Building your first application – Steps Involved • Run Microsoft Visual Studio.NET.

4. Building your first application – Steps Involved • In start page click New Project.

5. Building your first application – Steps Involved • In the New Project dialog box select Project Types: Visual C# Projects. Under Templates select Empty Project

6. Building your first application – Steps Involved • Right click References in the Solution Explorer and add reference to the following files. System.dll System.Drawing.dll System.Windows.Forms.dll

7. Building your first application – Steps Involved • The following dialog box pops up

8. Building your first application – Steps Involved • Click on file and New Item Menu Select Local Project Items from categories and Code File from templates. This step is very essential as it dissuades Visual Studio.NET from generating code for us

9. Building your first application – Steps Involved • Add New Item Dialog Box:

10. Building your first application – Steps Involved • We are all set to write code now

11. The Message Box • MessageBox class - Displays a Message Box that contains Text,Buttons and Symbols that inform and instruct the user. • MessageBox is derived from Object - Inherits a few methods implemented by Object • MessageBox implements static method Show

12. The Show method has 12 different versions. • Here a few ways of using the Show method - DialogResult Show(string strTxt); - DialogResult Show(string strTxt, string strCaption); - DialogResult Show(string strTxt, string strCaption MessageBoxButtons mbb); - DialogResult Show(string strTxt, string strCaption MessageBoxButtons mbb, MessageBoxIcon mbi); MessageBox

13. Message Box • An example of MessageBox class and Show method. using System; using System.Windows.Forms; class MessageBoxHelloworld { public static void Main() { MessageBox.Show("Hello world", "Minu is the best",MessageBoxButtons.OKCancel,MessageBoxIcon.Exclamation,Mes sageBoxDefaultButton.Button2); } } • Note the following. -Systems.Windows.Form is a namespace. -MessageBox is a class in that namespace. -Show is a static method in the MessageBox class,hence prefaced with the class name .

14. Message Box • Output of Previous code.

15. Message Box • MessageBoxButtons Enumeration. OK--------------------0 OK, Cancel-----------1 Abort, Retry, Ignore2 Yes, No, Cancel------3 Yes, No---------------4 Retry, Cancel--------5

16. Message Box • MessageBoxIcon Enumeration. None----------0x00 Hand-----------0x10 Question-------0x20 Warning--------0x30

17. Message Box • MessageBoxDefaultButton Enumeration. Button1----------0x000 Button2-----------0x100 Button3----------0x200

18. Message Box • Returning values from a MessageBox In .NET MessageBox returns one of the DialogResult enumerated values, again corresponding to the button which was clicked. None-----------------0 OK--------------------1 Cancel----------------2 Abort-----------------3 Retry----------------4 Ignore----------------5 Yes ------------------6 No--------------------7

19. Message Box • Returning values from a MessageBox DialogResult dr; dr=MessageBox.Show("Click a button", "", MessageBoxButtons.YesNoCancel); if (dr==DialogResult.Yes) { // code for Yes here } else if (dr=DialogResult.No) { // code for No here } else { // code for Cancel here }

20. The Form A WINDOW in Windows Programming is called a FORM in .NET Framework - Caption Bar(Title Bar) - Menu Bar - Client area - A sizing border

21. The Form A Form is a class in the System.Windows.Forms namespace A new instance of the Form class is made by using the new operator – 1. new System.Windows.Forms.Form(); 2. using namespace System.Windows.Forms; new Form(); 4. using namespace System.Windows.Forms; Form myForm; 3. using namespace System.Windows.Forms; Form myForm = new Form();

22. Show Form • To make form visible : form.Visible = true; form.Show(); • To make form invisible : form.Visible = false; form.Hide();

23. Application.Run method • Application.Run(form) causes the program to enter a message loop and that the form passed to the Run method is equipped with the code to post a quit message to the message loop when the form is closed. • When you close a form passed as an argument to the Run method, it closes all the other forms created by the program. • If a form is not passed as an argument to the Run method, the program need to explicitly call the Application.Exit method to force the Application.Run to return

24. Form properties class FormProperties { public static void Main() { Form form = new Form(); form.Text = "Form Properties"; form.BackColor = Color.BlanchedAlmond; form.Width *= 2; form.Height /= 2; form.FormBorderStyle = FormBorderStyle.FixedSingle; form.MaximizeBox = false; form.Cursor = Cursors.Hand; form.StartPosition = FormStartPosition.CenterScreen; Application.Run(form); } }

25. Events • All input is associated with an EVENT. • Everything that the program does, after the form initialization, is in response to an event. • For most of the time program sits dormant somewhere inside the Application.Run call, waiting for an event to happen. • An event handler is the method to process an event. • The arguments of the handler match a function prototype definition called a DELEGATE

26. Handling the Paint Event • PaintEventHandler is a delegate defined in Systems.Windows.Forms namespace as follows : public delegate void PaintEventHandler(object objSender, PaintEventArgs pea); • To handle paint events in the program a static method should be defined in your class static void MyPaintHandler(object objSender, PaintEventArgs pea) { } • Add the handler to the Paint event of the Form class form.Paint += new PaintEventHandler(MyPaintHandler);

27. Inheriting Form class • Customization • Extensibility

28. Inheriting Form class class InheritTheForm: Form { public static void Main() { InheritTheForm form = new InheritTheForm(); form.Text = "Inherit the Form"; form.BackColor = Color.White; Application.Run(form); } }

29. Inheriting Form class class InheritWithConstructor: Form { public static void Main() { Application.Run(new InheritWithConstructor()); } public InheritWithConstructor() { Text = "Inherit with Constructor"; BackColor = Color.White; } }

30. Inheriting Form class • One advantage of inheriting from Form class is that not only the derived class has access to the Form classes public functions but also to its protected ones. • One such protected method is OnPaint. • We don’t want to call this method but override it. • If we override OnPaint we don’t need to install a Paint event handler. protected override void OnPaint(PaintEventArgs pea) { base.OnPaint(pea); Graphics grfx = pea.Graphics; grfx.DrawString("Hello, Windows Forms!", Font, Brushes.Black, 0, 0); }

31. Inheriting Form class class HelloWorld: Form { public static void Main() { Application.Run(new HelloWorld()); } public HelloWorld() { Text = "Hello World"; BackColor = Color.White; } protected override void OnPaint(PaintEventArgs pea) { Graphics grfx = pea.Graphics; grfx.DrawString("Hello, Windows Forms!", Font, Brushes.Black, 0, 0); } }