Dr. Catherine Stringfellow
Dr. Stewart Carpenter

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 In both C++ and C#, one can develop
Console and Windows applications
 Window apps in C++ use MFCs, in C# use the FCL for the .NET platform
 FCL is composed of many namespaces using System.Windows.Forms;

 if, if-else, switch similar to C++
 Loops similar to C++
 But there is a foreach for arrays

 Class Math is located in namespace
System (unnecessary to add an assembly reference)
 Using methods of static classes
 ClassName.MethodName( argument1, arument2 , … )
 Example:
Math.Sqrt (900.0)
 Constants
 Math.PI
= 3.1415926535…

 Implicit Conversion
 Coercion of arguments to a higher type when passed to methods or in mixed-type expressions;
 Explicit Conversion
 Done with cast or class Convert in namespace
System
 Cast Example: int result = Square ( ( int ) y );

 Value types
 Contain data of the specified type

Built in types (int, float, double,…)
 Programmer created struct s and enumerations
 Reference types
 Contain an address
 Built-in ( array, object and string )
 Programmer created – Classes, Interfaces and Delegates

 Value types are passed by value and reference types are passed by reference by default
 To pass a value type by reference so you can modify the original variable?


Use the ref keyword
• with variables already initialized
Use the out keyword
• when the called method will initialize it

 Must use new operator to allocate dynamically the number of elements in the array int [] x; // declare reference to an array x = new int [ 10 ]; // dynamically allocate array

 Since sorting data is important in many applications, .NET Framework includes high-speed sorting capabilities
// sort elements in array a
Array.Sort( x );
// Determine number of elements in x by property x.Length

 Rectangular arrays – syntax a little different from C++
 Jagged Arrays
 An array of arrays of different lengths

// declaration of rectangular array int [,] array1 = new int [5,10];
// declaration and initialization of jagged array int [][] array2 = new int [ 3 ][]; array2[ 0 ] = new int [] { 1 , 2 }; array2[ 1 ] = new int [] { 3 }; array2[ 2 ] = new int [] { 4 , 5 , 6 };

 The foreach repetition structure is used to iterate through values in arrays
 No counter
 A variable is used to represent the value of each element foreach ( int grade in gradeArray )
{ if ( grade < lowGrade ) lowGrade = grade;
}

 If the constructor does not explicitly initialize data members, the data members are initialized by default


Primitive numeric types are set to 0
Boolean types are set to false
 Reference types are set to null

 Public properties allow clients to:
 Get (obtain the values of) private data
• and may control formatting and display
 Set (assign values to) private data
• and may scrutinize attempts to modify value

class Time
{ private int hour;
// property Hour public int Hour
{ get
{ return hour; }
} set
{ hour = ( ( value >= 0 && value < 24 ) ? value : 0 ); }
}
Use it in caller as cout << time.Hour; or time.Hour = 5;

 When objects are no longer referenced, the
CLR performs garbage collection
 Use finalizer s in conjunction with the garbage collector to release resources (database connections, file access, etc.) explicitly

 Everyone in C#.NET community uses
ToString to obtain an object’s string representation.
//Method of class Point to return string representation of Point public override string ToString ( )
{ return “(" + x + ", " + y + “)" ;
}
// call method to display new point value string output += "\n\nThe new location of point is " + point;

Other “interesting” variations from familiar C++ constructs

 abstract classes use keyword abstract sealed classes that cannot be overridden

Interface s use inheritance notation


Delegate s provide mechanism for passing method references
Exception handling includes a finally block to release resources