C# and.net (1) cont d

Transcription

1 C# and.net (1) cont d Acknowledgements and copyrights: these slides are a result of combination of notes and slides with contributions from: Michael Kiffer, Arthur Bernstein, Philip Lewis, Hanspeter Mφssenbφck, Hanspeter Mφssenbφck, Wolfgang Beer, Dietrich Birngruber, Albrecht Wφss, Mark Sapossnek, Bill Andreopoulos, Divakaran Liginlal, Michael Morrison, Anestis Toptsis, Deitel and Associates, Prentice Hall, Addison Wesley, Microsoft AA. They serve for teaching purposes only and only for the students that are registered in CSE4413 and should not be published as a book or in any form of commercial product, unless written permission is obtained from each of the above listed names and/or organizations. 1

2 C# Namespaces Namespace A group of classes and their methods No two classes in the same namespace may have the same name Classes in different namespaces may have the same name The Framework Class Library (FCL) is composed of namespaces Namespaces are stored in.dll files called assemblies A list of the FCL namespaces are shown next Included in a program with the using keyword 2

3 C# Namespaces Namespace System System.Data System.Drawing System.IO System.Threading System.Windows.Forms System.Xml Description Contains essential classes and data types (such as int, double, char, etc.). Implicitly referenced by all C# programs. Contains classes that form ADO.NET, used for database access and manipulation. Contains classes used for drawing and graphics. Contains classes for the input and output of data, such as with files. Contains classes for multithreading, used to run multiple parts of a program simultaneously. Contains classes used to create graphical user interfaces. Contains classes used to process XML data. Some of the namespaces of the Framework Class Library 3

4 How to create a namespace Create a class library project (in VS.NET) (File -> New -> New Project -> [C# Projects selected in Project types] -> Class Library). Make sure that namespace TimeLibrary is included in the beginning of the generated file. (as shown in next slide). 4

5 Namespaces and Assemblies Simple Class Library. 5

6 How to create a namespace, cont d Type your code for the class (you may rename the class, as you like). Compile the code with the Build Solution option (Build -> Build Solution). This code cannot be executed since it doesn t contain Main(), but it will generate a.dll file, named TimeLibrary.dll, found in the bin\debug directory under your project directory (TimeLibrary). This.dll file is the Assembly and it can then be included in your applications (by typing using TimeLibrary at the beginning of your files. 6

7 1 // AssemblyTest.cs 2 // Using class Time3 from assembly TimeLibrary. 3 4 using System; 5 using TimeLibrary; 6 7 // AssemblyTest class definition 8 class AssemblyTest 9 { 10 // main entry point for application 11 static void Main( string[] args ) 12 { 13 Time3 time = new Time3( 13, 27, 6 ); Console.WriteLine( 16 "Standard time: {0}\nUniversal time: {1}\n", 17 time.tostandardstring(), time.touniversalstring() ); 18 } 19 } AssemblyTest.cs Use Time3 as usual Reference the TimeLibrary namespace Program Output Standard time: 1:27:06 PM Universal time: 13:27:06 7

8 Indexers Allow usage of objects using array notation. Borrowed from C++ ability to overload the [] operator (not possible in C#, or in Java). Allows using objects, like this: obj[0], to mean obj.getx(), if index 0 refers to instance variable x. obj[0] = 7 to mean obj.setx(7). The indexes 0, 1, 2, refer to instance variables of the class of object obj. Index 0 refers to first instance variable, index 1 refers to second instance variable, etc. 8

9 Indexer to refer to instance vars lb and oz (index 0 refers to lb, 1 refers to oz) 9

10 Usage of indexer of Weight this[0] returns the value of lb. ( and, likewise, w[0] would also refer to lb of w, where w is an object of type Weight.) 10

11 Indexer to refer to instance var somearray. (index 0 refers to somearray[0], 1 refers to somearray[1], etc) 11

12 Usage of indexer of Weight and MyArray 12

13 13

14 Exceptions. In C# are pretty much as in Java. 14

15 With no exception handling. (Method2() is in a class ExceptionsDemo) 15

16 Output (crash) 16

17 With exception handling 17

18 Main() to invoke Method1() 18

19 Output (no exception occurred. Finally executed though) 19

20 Output (exception occurred. Finally still executed) 20

21 Passing Arguments to methods: C# supports both Call-By-Value and pass and Call-By-Reference Passing by value (same as Java) Send a method a copy of the object When returned are always returned by value Set by value by default Passing by reference (same as passing a pointer in C, C++) Send a method the actual reference point Causes the variable to be changed throughout the program When returned are always returned by reference The ref keyword specifies by reference The out keyword means a called method will initialize it 21

22 1 // RefOutTest.cs 2 // Demonstrating ref and out parameters. 3 4 using System; 5 using System.Windows.Forms; 6 7 class RefOutTest 8 { 9 // x is passed as a ref int (original value will change) 10 static void SquareRef( ref int x ) 11 { 12 x = x * x; 13 } // original value can be changed and initialized 16 static void SquareOut( out int x ) 17 { 18 x = 6; 19 x = x * x; 20 } // x is passed by value (original value not changed) 23 static void Square( int x ) 24 { 25 x = x * x; 26 } static void Main( string[] args ) 29 { 30 // create a new integer value, set it to 5 31 int y = 5; 32 int z; // declare z, but do not initialize it 33 RefOutTest.cs 22

23 34 // display original values of y and z 35 string output1 = "The value of y begins as " 36 + y + ", z begins uninitialized.\n\n\n"; // values of y and z are passed by by value reference 39 RefOutTest.SquareRef( ref y ); 40 RefOutTest.SquareOut( out z ); // display values of y and z after modified by methods 43 // SquareRef and SquareOut 44 string output2 = "After calling SquareRef with y as an " + 45 "argument and SquareOut with z as an argument,\n" + 46 "the values of y and z are:\n\n" + 47 "y: " + y + "\nz: " + z + "\n\n\n"; // values of y and z are passed by by value 50 RefOutTest.Square( y ); 51 RefOutTest.Square( z ); // values of y and z will be same as before because Square 54 // did not modify variables directly 55 string output3 = "After calling Square on both x and y, " + 56 "the values of y and z are:\n\n" + 57 "y: " + y + "\nz: " + z + "\n\n"; MessageBox.Show( output1 + output2 + output3, 60 "Using ref and out Parameters", MessageBoxButtons.OK, 61 MessageBoxIcon.Information ); } // end method Main } // end class RefOutTest RefOutTest.cs 23

24 RefOutTest.cs Program Output 24

25 const and readonly Members Declare constant members (members whose value will never change) using the keyword const (equivalent to java s final) const members are implicitly static const members must be initialized when they are declared Use keyword readonly to declare members who will be initialized in the constructor but not change after that 25

26 1 // UsingConstAndReadOnly.cs 2 // Demonstrating constant values with const and readonly. 3 4 using System; 5 7 // Constants class definition 8 public class Constants 9 { 10 // PI is constant variable 11 public const double PI = ; // radius is a constant variable 14 // that is uninitialized 15 public readonly int radius; public Constants( int radiusvalue ) 18 { 19 radius = radiusvalue; 20 } 22 } // end class Constants UsingConstAndReadOnly.cs Constant variable PI Readonly variable radius; must be initialized in constructor Initialize readonly member radius 26

27 UsingConstAndReadOnly.cs 1 // UsingConstAndReadOnly.cs 2 // Demonstrating constant values with const and readonly // UsingConstAndReadOnly class definition 25 public class UsingConstAndReadOnly 26 { 27 // method Main creates Constants 28 // object 29 static void Main( string[] args ) 30 { 31 Random random = new Random(); Constants constantvalues = 34 new Constants( random.next( 1, 20 ) ); 35 27

28 UsingConstAndReadOnly.cs 36 MessageBox.Show( "Radius = " + constantvalues.radius + 37 "\ncircumference = " * Constants.PI * constantvalues.radius, 39 "Circumference" ); } // end method Main } // end class UsingConstAndReadOnly Output from two separate runs 28

29 Arrays 29

30 1 // SumArray.cs 2 // Computing the sum of the elements in an array. 3 4 using System; 5 using System.Windows.Forms; 6 7 class SumArray 8 { 9 // main entry point for application 10 static void Main( string[] args ) 11 { 12 int[] a = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 13 int total = 0; for ( int i = 0; i < a.length; i++ ) 16 total += a[ i ]; MessageBox.Show( "Total of array elements: " + total, 19 "Sum the elements of an array", 20 MessageBoxButtons.OK, MessageBoxIcon.Information ); } // end Main } // end class SumArray Declare integer array a and initialize it Total the contents of array a 30

31 Passing Arrays to Methods Pass arrays as arguments to methods by specifying the name of the array (no brackets) Arrays are passed by reference Individual array elements are passed by value 31

32 1 // Fig. 7.8: PassArray.cs 2 // Passing arrays and individual elements to methods. 3 using System; 4 using System.Drawing; 5 using System.Collections; 6 using System.ComponentModel; 7 using System.Windows.Forms; 8 using System.Data; 9 10 public class PassArray : System.Windows.Forms.Form 11 { 12 private System.Windows.Forms.Button showoutputbutton; 13 private System.Windows.Forms.Label outputlabel; // Visual Studio.NET generated code [STAThread] 18 static void Main() 19 { 20 Application.Run( new PassArray() ); 21 } private void showoutputbutton_click( object sender, 24 System.EventArgs e ) 25 { 26 int[] a = { 1, 2, 3, 4, 5 }; outputlabel.text = "Effects of passing entire array " + 29 "call-by-reference:\n\nthe values of the original " + 30 "array are:\n\t"; for ( int i = 0; i < a.length; i++ ) 33 outputlabel.text += " " + a[ i ]; ModifyArray( a ); // array is passed by reference Declare and initialize integer array a PassArray.cs Call method ModifyArray, pass array a as an argument by reference Output contents of array a 32

33 36 37 outputlabel.text += 38 "\n\nthe values of the modified array are:\n\t"; // display elements of array a 41 for ( int i = 0; i < a.length; i++ ) 42 outputlabel.text += " " + a[ i ]; outputlabel.text += "\n\neffects of passing array " + 45 "element call-by-value:\n\na[ 3 ] before " + 46 "ModifyElement: " + a[ 3 ]; // array element passed call-by-value 49 ModifyElement( a[ 3 ] ); outputlabel.text += 52 "\na[ 3 ] after ModifyElement: " + a[ 3 ]; 53 } // method modifies the array it receives, 56 // original will be modified 57 public void ModifyArray( int[] b ) 58 { 59 for ( int j = 0; j < b.length; j++ ) 60 b[ j ] *= 2; 61 } // method modifies the integer passed to it 64 // original will not be modified 65 public void ModifyElement( int e ) 66 { 67 outputlabel.text += 68 "\nvalue received in ModifyElement: " + e; 69 Replace every element in array by twice its value PassArray.cs Output array a after ModifyArray changed the contents Call method ModifyElement, pass element of array a that is at index 3 33

34 PassArray.cs 70 e *= 2; outputlabel.text += 73 "\nvalue calculated Multiply in argument by two ModifyElement: " + e; This does not change value of element in original 74 } array, because the element was passed by value 75 } 34

35 Passing Arrays by Value and by Reference Variables that store object, actually store references to those objects A reference is a location in computer s memory where the object itself is stored Passing value types to methods A copy of the variable is made Any changes to variable in method do not effect the original variable Passing reference types to methods A copy of the reference to the object is made Any changes to the reference in the method do not effect the original variable Any changes to the contents of the object in the method, do effect the object outside the method 35

36 Passing Arrays by Value and by Reference Keyword ref may be used to pass arguments to method by reference Value type variables are not copied modifying the variable in the method will modify the variable outside the method References to objects are not copied modifying the reference in the method will modify the reference outside the method Programmers have to be careful when using ref May lead to references being set to null May lead to methods modifying variable values and references in ways that are not desired 36

37 1 // ArrayReferenceTest.cs 2 // Testing the effects of passing array references 3 // by value and by reference. 4 using System; 5 using System.Drawing; 6 using System.Collections; 7 using System.ComponentModel; 8 using System.Windows.Forms; 9 using System.Data; public class ArrayReferenceTest : System.Windows.Forms.Form 12 { 13 private System.Windows.Forms.Label outputlabel; 14 private System.Windows.Forms.Button showoutputbutton; [STAThread] 17 static void Main() 18 { 19 Application.Run( new ArrayReferenceTest() ); 20 } private void showoutputbutton_click( object sender, 23 System.EventArgs e ) 24 { 25 // create and initialize firstarray 26 int[] firstarray = { 1, 2, 3 }; // copy firstarray reference 29 int[] firstarraycopy = firstarray; outputlabel.text += 32 "Test passing firstarray reference by value"; outputlabel.text += "\n\ncontents of firstarray " + 35 "before calling FirstDouble:\n\t"; ArrayReferenceTest.cs Declare and initialize integer array firstarray Declare integer array firstarraycopy and have it reference firstarray 37

38 36 37 // print contents of firstarray 38 for ( int i = 0; i < firstarray.length; i++ ) 39 outputlabel.text += firstarray[ i ] + " "; // pass reference firstarray by value to FirstDouble 42 FirstDouble( firstarray ); outputlabel.text += "\n\ncontents of firstarray after " + 45 "calling FirstDouble\n\t"; // print contents of firstarray 48 for ( int i = 0; i < firstarray.length; i++ ) 49 outputlabel.text += firstarray[ i ] + " "; // test whether reference was changed by FirstDouble 52 if ( firstarray == firstarraycopy ) 53 outputlabel.text += 54 "\n\nthe references refer to the same array\n"; 55 else 56 outputlabel.text += 57 "\n\nthe references refer to different arrays\n"; // create and initialize secondarray 60 int[] secondarray = { 1, 2, 3 }; // copy secondarray reference 63 int[] secondarraycopy = secondarray; outputlabel.text += "\ntest passing secondarray " + 66 "reference by reference"; outputlabel.text += "\n\ncontents of secondarray " + 69 "before calling SecondDouble:\n\t"; 70 ArrayReferenceTest.cs Test whether firstarray and firstarraycopy reference the same object Declare integer array secondarraycopy and set it to reference Output secondarray contents of firstarray Declare and initialize integer array secondarray Call method FirstDouble on firstarray Output contents of firstarray 38

39 71 // print contents of secondarray before method call 72 for ( int i = 0; i < secondarray.length; i++ ) 73 outputlabel.text += secondarray[ i ] + " "; SecondDouble( ref secondarray ); 76 Test whether secondarray and secondarraycopy reference the same object 77 outputlabel.text += "\n\ncontents of secondarray " + 78 "after calling SecondDouble:\n\t"; // print contents of secondarray after method call 81 for ( int i = 0; i < secondarray.length; i++ ) 82 outputlabel.text += secondarray[ i ] + " "; // test whether reference was changed by SecondDouble 85 if ( secondarray == secondarraycopy ) 86 outputlabel.text += 87 "\n\nthe references refer to the same array\n"; 88 else 89 outputlabel.text += 90 "\n\nthe references refer to different arrays\n"; } // end method showoutputbutton_click // modify elements of array and attempt to modify 95 // reference 96 void FirstDouble( int[] array ) 97 { 98 // double each element's value 99 for ( int i = 0; i < array.length; i++ ) 100 array[ i ] *= 2; // create new reference and assign it to array 103 array = new int[] { 11, 12, 13 }; 104 } 105 ArrayReferenceTest.cs Replace each element in the array Output by twice contents its value of secondarray Set array to reference a new integer array containing the values Call method 11, 12 and SecondDouble 13 and pass secondarray by reference Output contents of secondarray 39

40 ArrayReferenceTest.cs 106 // modify elements of array and change reference array 107 // to refer to a new array 108 void SecondDouble( ref int[] array ) 109 { 110 // double each element's value 111 for ( int i = 0; i < array.length; i++ ) 112 array[ i ] *= 2; // create new reference and assign it to array 115 array = new int[] { 11, 12, 13 }; 116 } 117 } Replace each element in the array Set array by to twice reference its value a new integer array containing the values 11, 12 and 13 Program Output 40

41 foreach Repetition Structure The foreach repetition structure is used to iterate through values in data structures such as arrays No counter A variable is used to represent the value of each element 41

42 1 // ForEach.cs 2 // Demonstrating for/each structure. 3 using System; 4 5 class ForEach 6 { 7 // main entry point for the application 8 static void Main( string[] args ) 9 { 10 int[,] gradearray = { { 77, 68, 86, 73 }, 11 { 98, 87, 89, 81 }, { 70, 90, 86, 81 } }; int lowgrade = 100; foreach ( int grade in gradearray ) 16 { 17 if ( grade < lowgrade ) 18 lowgrade = grade; 19 } Console.WriteLine( "The minimum grade is: " + lowgrade ); 22 } 23 } The minimum grade is: 68 ForEach.cs Use the foreach loop to examine each element in the array If the current array element is smaller than lowgrade, set lowgrade to contain the value of the current element 42

43 Inheritance 43

44 1 // Point3.cs 2 // Point3 class represents an x-y coordinate pair. 4 using System; 6 // Point3 class definition implicitly inherits from Object 7 public class Point3 8 { 9 // point coordinate 10 private int x, y; 12 // default constructor 13 public Point3() 14 { 15 // implicit call to Object constructor occurs here 16 } // constructor 19 public Point3( int xvalue, int yvalue ) 20 { 21 // implicit call to Object constructor occurs here 22 X = xvalue; // use property X 23 Y = yvalue; // use property Y 24 } // property X 27 public int X 28 { 29 get 30 { 31 return x; 32 } 33 Declare coordinates as private Point3.cs 44

45 34 set 35 { 36 x = value; // no need for validation 37 } } // end property X // property Y 42 public int Y 43 { 44 get 45 { 46 return y; 47 } set 50 { 51 y = value; // no need for validation 52 } } // end property Y // return string representation of Point3 57 public override string ToString() 58 { 59 return "[" + X + ", " + Y + "]"; 60 } } // end class Point3 Methods to set x and y coordinates Point3.cs Overridden ToString method 45

46 1 // Circle4.cs 2 // Circle4 class that inherits from class Point3. 4 using System; 6 // Circle4 class definition inherits from Point3 7 public class Circle4 : Point3 8 { 9 private double radius; // default constructor 12 public Circle4() 13 { 14 // implicit call to Point constructor occurs here 15 } 17 // constructor 18 public Circle4( int xvalue, int yvalue, double radiusvalue ) 19 : base( xvalue, yvalue ) 20 { 21 Radius = radiusvalue; 22 } 24 // property Radius 25 public double Radius 26 { 27 get 28 { 29 return radius; 30 } 32 set 33 { 34 if ( value >= 0 ) // validation needed 35 radius = value; Constructor with implicit call to base class constructor Circle4.cs Constructor with explicit call to base class constructor Explicit call to base class constructor 46

47 36 } 38 } // end property Radius // calculate Circle diameter 41 public double Diameter() 42 { 43 return Radius * 2; // use property Radius 44 } // calculate Circle circumference 47 public double Circumference() 48 { 49 return Math.PI * Diameter(); 50 } // calculate Circle area 53 public virtual double Area() 54 { Method area declared virtual so it can be overridden 55 return Math.PI * Math.Pow( Radius, 2 ); // use property 56 } // return string representation of Circle4 59 public override string ToString() 60 { 61 // use base reference to return Point string representation 62 return "Center= " + base.tostring() + 63 "; Radius = " + Radius; // use property Radius 64 } 66 } // end class Circle4 Circle4.cs Circle4 s ToString method overrides Point3 s ToString method Call Point3 s ToString method to display coordinates 47

48 1 // CircleTest4.cs 2 // Testing class Circle4. 4 using System; 5 using System.Windows.Forms; 7 // CircleTest4 class definition 8 class CircleTest4 9 { 10 // main entry point for application 11 static void Main( string[] args ) 12 { 13 // instantiate Circle4 14 Circle4 circle = new Circle4( 37, 43, 2.5 ); // get Circle4's initial x-y coordinates and radius 17 string output = "X coordinate is " + circle.x + "\n" + 18 "Y coordinate is " + circle.y + "\n" + 19 "Radius is " + circle.radius; Change coordinates and radius of Circle4 object 21 // set Circle4's x-y coordinates and radius to new values 22 circle.x = 2; 23 circle.y = 2; 24 circle.radius = 4.25; 26 // display Circle4's string representation 27 output += "\n\n" + 28 "The new location and radius of circle are " + 29 "\n" + circle + "\n"; // display Circle4's Diameter 32 output += "Diameter is " + 33 String.Format( "{0:F}", circle.diameter() ) + "\n"; 34 CircleTest4.cs Create new Circle4 object Implicit call to Circle4 s ToString method 48

49 35 // display Circle4's Circumference 36 output += "Circumference is " + 37 String.Format( "{0:F}", circle.circumference() ) + "\n"; // display Circle4's Area 40 output += "Area is " + 41 String.Format( "{0:F}", circle.area() ); MessageBox.Show( output, "Demonstrating Class Circle4" ); } // end method Main } // end class CircleTest4 CircleTest4.cs Call Circle s Circumference and Area methods for output 49

50 sealed Classes and Methods sealed is a keyword in C# (equivalent to final in Java) sealed methods cannot be overridden in a derived class Methods that are declared static and private, are implicitly sealed sealed classes cannot have any derived-classes Creating sealed classes can allow some runtime optimizations e.g., virtual method calls can be transformed into non-virtual method calls 50

51 Building Graphical User Interfaces Graphical user interface Allow interaction with program visually Give program distinct look and feel Built from window gadgets Is an object, accessed via keyboard or mouse 51

52 Some GUI components Frame TextBox Menu Bar Scrollbar Button 52

53 Using VS.NET to build a windows application (GUI) 53

54 After selecting OK 54

55 Run by selecting Debug Start Without Debugging 55

56 Can choose View Code or View Designer Design view 56

57 Can open the toolbox while in design view. 57

58 Select any component from toolbox The GUI components available in C#. Select and drag into the design Form 58

59 Drag the component inside the Form (or click in the Form after having clicked on the component) A Button has been selected from the Toolbox and placed into the Form 59

60 Inside the Form select the button and right-click get properties menu Use these to adjust the properties of the component (e.g., font used, background color, etc). 60

61 Adding events Select this to add events 61

62 Generating the event code Click is one of the available Events for Button. Double click on Click and VS will generate the event code. 62

63 The generated event related code All this code has been generated by VS.NET Programmer fills in this part 63

64 Introduction Control Label TextBox Button CheckBox ComboBox ListBox Panel ScrollBar Description An area in which icons or uneditable text can be displayed. An area in which the user inputs data from the keyboard. The area also can display information. An area that triggers an event when clicked. A GUI control that is either selected or not selected. A drop-down list of items from which the user can make a selection, by clicking an item in the list or by typing into the box, if permitted. An area in which a list of items is displayed from which the user can make a selection by clicking once on any element. Multiple elements can be selected. A container in which components can be placed. Allows the user to access a range of values that cannot normally fit in its container. Some basic GUI components. 64

65 Windows Forms WinForms Create GUIs for programs Element on the desktop Represented by: Dialog Window MDI window 65

66 Basic Event Handling List of events supported by control Events icon Selected event Current even handler (none) Event description Events section of the Properties window. 66

67 1 // SimpleEventExample.cs 2 // Using Visual Studio.NET to create event handlers. 4 using System; 5 using System.Drawing; 6 using System.Collections; 7 using System.ComponentModel; 8 using System.Windows.Forms; 9 using System.Data; 11 // program that shows a simple event handler 12 public class MyForm : System.Windows.Forms.Form 13 { 14 private System.ComponentModel.Container components = null; // Visual Studio.NET generated code 18 [STAThread] 19 static void Main() 20 { 21 Application.Run( new MyForm() ); 22 } 24 // Visual Studio.NET creates an empty handler, 25 // we write definition: show message box when form clicked 26 private void MyForm_Click( object sender, System.EventArgs e ) 27 { 28 MessageBox.Show( "Form was pressed" ); 29 } } // end class MyForm SimpleEventExample.cs 67

68 Labels, TextBoxes and Buttons Labels Provide text instruction Read only text Defined with class Label Derived from class Control Textbox Class TextBox Area for text input Password textbox Button Control to trigger a specific action Checkboxes or radio buttons Derived from ButtonBase 68

69 Labels TextBoxes and Buttons Label Properties Common Properties Font Text TextAlign Description / Delegate and Event Arguments The font used by the text on the Label. The text to appear on the Label. The alignment of the Label s text on the control. One of three horizontal positions (left, center or right) and one of three vertical positions (top, middle or bottom). Label properties. 69

70 Labels TextBoxes and Buttons TextBox Properties and Events Common Properties Description / Delegate and Event Arguments AcceptsReturn Multiline PasswordChar ReadOnly ScrollBars Text Common Events TextChanged TextBox properties and events. If true, pressing Enter creates a new line if textbox spans multiple lines. If false, pressing Enter clicks the default button of the form. If true, textbox can span multiple lines. Default is false. Single character to display instead of typed text, making the TextBox a password box. If no character is specified, Textbox displays the typed text. If true, TextBox has a gray background and its text cannot be edited. Default is false. For multiline textboxes, indicates which scrollbars appear (none, horizontal, vertical or both). The text to be displayed in the text box. (Delegate EventHandler, event arguments EventArgs) Raised when text changes in TextBox (the user added or deleted characters). Default event when this control is double clicked in the designer. 70

71 Labels TextBoxes and Buttons Button properties and events Common Properties Text Common Events Click Button properties and events. Description / Delegate and Event Arguments Text displayed on the Button face. (Delegate EventHandler, event arguments EventArgs) Raised when user clicks the control. Default event when this control is double clicked in the designer. 71

72 Text area (a Textbox with properties Multiline and AcceptsReturn set to true. 72

73 An example GUI Textbox in which can type password Password displayed upon clicking button 73

74 using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; namespace WindowsApplication3_2 { /// <summary> /// Summary description for Form1. /// </summary> public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.TextBox textbox1; private System.Windows.Forms.Label label1; private System.Windows.Forms.Button button1; /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.Container components = null; public Form1() { // // Required for Windows Form Designer support // InitializeComponent(); The code Declared components // // TODO: Add any constructor code after InitializeComponent call // } 74

75 private void InitializeComponent() { this.textbox1 = new System.Windows.Forms.TextBox(); this.label1 = new System.Windows.Forms.Label(); this.button1 = new System.Windows.Forms.Button(); this.suspendlayout(); // // textbox1 // this.textbox1.location = new System.Drawing.Point(32, 48); this.textbox1.name = "textbox1"; this.textbox1.passwordchar = '*'; this.textbox1.size = new System.Drawing.Size(176, 20); this.textbox1.tabindex = 0; this.textbox1.text = ""; this.textbox1.textchanged += new System.EventHandler(this.textBox1_TextChanged); // Event handler for textbox, but never // label1 used. (added automatically by vs.net) // this.label1.backcolor = System.Drawing.SystemColors.Info; this.label1.location = new System.Drawing.Point(32, 96); this.label1.name = "label1"; this.label1.size = new System.Drawing.Size(176, 23); 75 this.label1.tabindex = 1; Construct components Set property so that chars appear as * when typed in textbox1.

76 // // button1 // this.button1.location = new System.Drawing.Point(48, 144); this.button1.name = "button1"; this.button1.size = new System.Drawing.Size(152, 23); this.button1.tabindex = 2; this.button1.text = "Show password"; this.button1.click += new System.EventHandler(this.button1_Click); // Event handler for button. (generated by vs // Form1.net, and implemented by programmer). // this.autoscalebasesize = new System.Drawing.Size(5, 13); this.clientsize = new System.Drawing.Size(292, 273); this.controls.addrange(new System.Windows.Forms.Control[] { this.button1, this.label1, this.textbox1}); this.name = "Form1"; this.text = "Form1"; this.resumelayout(false); } #endregion 76

77 /// <summary> /// Clean up any resources being used. /// </summary> protected override void Dispose( bool disposing ) { if( disposing ) { if (components!= null) { components.dispose(); } } base.dispose( disposing ); } private void button1_click(object sender, System.EventArgs e) { label1.text = textbox1.text; } private void textbox1_textchanged(object sender, System.EventArgs e) { This line added by programmer. } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> /// <summary> 77

78 /// The main entry point for the application. /// </summary> [STAThread] static void Main() { Application.Run(new Form1()); } } } 78

79 GroupBoxes and Panels Arrange components on a GUI GroupBoxes can display a caption Text property determines its caption Panels can have scrollbar View additional controls inside the Panel 79

80 GroupBoxes and Panels GroupBox Properties Common Properties Description Controls The controls that the GroupBox contains. Text Text displayed on the top portion of the GroupBox (its caption). GroupBox properties. 80

81 GroupBoxes and Panels Panel Properties Common Properties AutoScroll BorderStyle Controls Panel properties. Description Whether scrollbars appear when the Panel is too small to hold its controls. Default is false. Border of the Panel (default None; other options are Fixed3D and FixedSingle). The controls that the Panel contains. 81

82 Before any click. Example After click of button 1 Panel containing 2 buttons 82

83 using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; namespace WindowsApplication3_3 { /// <summary> /// Summary description for Form1. /// </summary> public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.GroupBox groupbox1; private System.Windows.Forms.Button button1; private System.Windows.Forms.Button button2; private System.Windows.Forms.Panel panel1; private System.Windows.Forms.Button button3; private System.Windows.Forms.Button button4; private System.Windows.Forms.Label label1; /// <summary> private System.ComponentModel.Container components = null; public Form1() { // // Required for Windows Form Designer support // InitializeComponent(); Declared components The code // // TODO: Add any constructor code after InitializeComponent call // } 83

84 //.. private void InitializeComponent() { this.groupbox1 = new System.Windows.Forms.GroupBox(); this.button1 = new System.Windows.Forms.Button(); this.button2 = new System.Windows.Forms.Button(); Construct this.panel1 = new System.Windows.Forms.Panel(); this.button3 = new System.Windows.Forms.Button(); components this.button4 = new System.Windows.Forms.Button(); this.label1 = new System.Windows.Forms.Label(); this.groupbox1.suspendlayout(); this.panel1.suspendlayout(); this.suspendlayout(); Configure // // groupbox1 // components. this.groupbox1.backcolor = System.Drawing.SystemColors.Desktop; this.groupbox1.controls.addrange(new System.Windows.Forms.Control[] { this.button2, this.button1}); this.groupbox1.font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(161))); this.groupbox1.location = new System.Drawing.Point(40, 32); this.groupbox1.name = "groupbox1"; this.groupbox1.size = new System.Drawing.Size(240, 96); this.groupbox1.tabindex = 0; this.groupbox1.tabstop = false; this.groupbox1.text = "GroupBox with 2 buttons"; Hookup to // // button1 // events this.button1.backcolor = System.Drawing.Color.Red; this.button1.font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(161))); this.button1.location = new System.Drawing.Point(16, 40); this.button1.name = "button1"; this.button1.size = new System.Drawing.Size(80, 32); this.button1.tabindex = 0; this.button1.text = "button1"; this.button1.click += new System.EventHandler(this.button1_Click); 84

85 // // button2 // this.button2.backcolor = System.Drawing.Color.Red; this.button2.font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(161))); this.button2.location = new System.Drawing.Point(144, 32); this.button2.name = "button2"; this.button2.size = new System.Drawing.Size(80, 32); this.button2.tabindex = 1; this.button2.text = "exit"; this.button2.click += new System.EventHandler(this.button2_Click); // // panel1 // this.panel1.backcolor = System.Drawing.SystemColors.Desktop; this.panel1.controls.addrange(new System.Windows.Forms.Control[] { this.button4, this.button3}); this.panel1.location = new System.Drawing.Point(40, 184); this.panel1.name = "panel1"; this.panel1.size = new System.Drawing.Size(224, 96); this.panel1.tabindex = 1; this.panel1.paint += new System.Windows.Forms.PaintEventHandler(this.panel1_Paint); // // button3 // this.button3.backcolor = System.Drawing.Color.FromArgb(((System.Byte)(0)), ((System.Byte)(0)), ((System.Byte)(192))); this.button3.font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(161))); this.button3.forecolor = System.Drawing.SystemColors.ControlLightLight; this.button3.location = new System.Drawing.Point(16, 48); this.button3.name = "button3"; this.button3.size = new System.Drawing.Size(80, 32); this.button3.tabindex = 0; this.button3.text = "button3"; this.button3.click += new System.EventHandler(this.button3_Click); 85

86 // // button4 // this.button4.backcolor = System.Drawing.Color.FromArgb(((System.Byte)(0)), ((System.Byte)(0)), ((System.Byte)(192))); this.button4.font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(161))); this.button4.forecolor = System.Drawing.SystemColors.ControlLightLight; this.button4.location = new System.Drawing.Point(136, 48); this.button4.name = "button4"; this.button4.size = new System.Drawing.Size(80, 32); this.button4.tabindex = 1; this.button4.text = "button4"; this.button4.click += new System.EventHandler(this.button4_Click); // // label1 // this.label1.backcolor = System.Drawing.Color.Yellow; this.label1.font = new System.Drawing.Font("Microsoft Sans Serif", 12F, (System.Drawing.FontStyle.Bold System.Drawing.FontStyle.Italic), System.Drawing.GraphicsUnit.Point, ((System.Byte)(161))); this.label1.location = new System.Drawing.Point(64, 144); this.label1.name = "label1"; this.label1.size = new System.Drawing.Size(168, 23); this.label1.tabindex = 2; this.label1.text = "no button pressed"; this.label1.textalign = System.Drawing.ContentAlignment.MiddleCenter; // // Form1 // this.autoscalebasesize = new System.Drawing.Size(5, 13); this.clientsize = new System.Drawing.Size(296, 317); this.controls.addrange(new System.Windows.Forms.Control[] { this.label1, this.panel1, this.groupbox1}); this.name = "Form1"; this.text = "Form1"; this.groupbox1.resumelayout(false); this.panel1.resumelayout(false); this.resumelayout(false); } #endregion. 86

87 /// <summary> /// The main entry point for the application. /// </summary> [STAThread] static void Main() { Application.Run(new Form1()); } private void panel1_paint(object sender, System.Windows.Forms.PaintEventArgs e) { }. Event handling for rendering the panel (automatically generated). Event handling code for the four buttons. private void button1_click(object sender, System.EventArgs e) { label1.text = "Button 1 pressed"; } private void button2_click(object sender, System.EventArgs e) { this.close(); } private void button3_click(object sender, System.EventArgs e) { label1.text = "Button 3 pressed"; } private void button4_click(object sender, System.EventArgs e) { label1.text = "Button 4 pressed"; } } } 87