Differences between C# and C++

1. Differences between C# and C++ Dr. Catherine Stringfellow Dr. Stewart Carpenter

2. .NET Framework Class Library and Namespaces • 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;

3. Control Structures • if, if-else, switch similar to C++ • Loops similar to C++ • But there is a foreach for arrays

4. Math Class • ClassMath 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…

5. Type Promotion • 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 );

6. Value and Reference Types • Value types • Contain data of the specified type • Built in types (int, float, double,…) • Programmer created - structs and enumerations • Reference types • Contain an address • Built-in (array, object and string) • Programmer created – Classes, Interfaces and Delegates

7. Passing Arguments by Value vs. by Reference • 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

8. Declaring Arrays • Must use new operator to allocate dynamically the number of elements in the array int[] x; // declare reference to an array x = newint[10]; // dynamically allocate array

9. Array Methods and Properties • 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

10. Multiple-Subscripted Arrays • Rectangular arrays – syntax a little different from C++ • Jagged Arrays • An array of arrays of different lengths

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

12. foreach Repetition Structure • 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; }

13. Initializing Class Objects: Constructors • 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

14. Properties • 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

15. classTime { 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;

16. Garbage Collection • When objects are no longer referenced, the CLR performs garbage collection • Use finalizers in conjunction with the garbage collector to release resources (database connections, file access, etc.) explicitly

17. ToString • 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 overridestring ToString ( ) { return“(" + x + ", " + y + “)"; } // call method to display new point value string output += "\n\nThe new location of point is " + point;

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