using System;
using System.Reflection;
public enum RegHives {
HKEY_CLASSES_ROOT,
HKEY_CURRENT_USER,
HKEY_LOCAL_MACHINE,
HKEY_USERS,
HKEY_CURRENT_CONFIG
}
public class RegKeyAttribute : Attribute {
public RegKeyAttribute(RegHives Hive, String ValueName) {
this.Hive = Hive;
this.ValueName = ValueName;
}
protected RegHives hive;
public RegHives Hive {
get { return hive; }
set { hive = value; }
}
protected String valueName;
public String ValueName {
get { return valueName; }
set { valueName = value; }
}
}
class SomeClass {
[RegKey(RegHives.HKEY_CURRENT_USER, "Foo")]
public int Foo;
public int Bar;
}
class Test {
[STAThread]
static void Main(string[] args) {
Type type = Type.GetType("FieldAttribs.SomeClass");
foreach (FieldInfo field in type.GetFields()) {
foreach (Attribute attr in
field.GetCustomAttributes(true)) {
RegKeyAttribute rka =
attr as RegKeyAttribute;
if (null != rka) {
Console.WriteLine("{0} will be saved in {1}{2}", field.Name, rka.Hive, rka.ValueName);
}
}
}
}
}
Class Interface
The super-string class.
using System;
public class MyString {
private string fString;
public MyString() {
fString = “”;
}
public MyString(string inStr) {
fString = inStr;
}
public string ToStr() {
return fString;
}
public string Right(int nChars) {
if (nChars > fString.Length)
return fString;
string s = “”;
for (int i = fString.Length – nChars; i < fString.Length; ++i)
s += fString[i];
return s;
}
public string Left(int nChars) {
if (nChars > fString.Length)
return fString;
string s = “”;
for (int i = 0; i < nChars; ++i)
s += fString[i];
return s;
}
public string Mid(int nStart, int nEnd) {
if (nStart < 0 || nEnd > fString.Length)
return fString;
if (nStart > nEnd)
return “”;
string s = “”;
for (int i = nStart; i < nEnd; ++i)
s += fString[i];
return s;
}
}
class Class1 {
static void Main(string[] args) {
MyString s = new MyString("Hello world");
System.Console.WriteLine("s = {0}", s.ToStr());
System.Console.WriteLine("Right 3 = [{0}]", s.Right(3));
System.Console.WriteLine("Left 6 = [{0}]", s.Left(6));
System.Console.WriteLine("Mid 2,4 = [{0}]", s.Mid(2, 4));
}
}
[/csharp]
change field value in a method
using System;
public class Foo
{
public int i;
}
class RefTest2App
{
public static void ChangeValue(Foo f)
{
f.i = 42;
}
static void Main(string[] args)
{
Foo test = new Foo();
test.i = 6;
Console.WriteLine("BEFORE METHOD CALL");
Console.WriteLine("test.i={0}", test.i);
Console.WriteLine();
ChangeValue(test);
Console.WriteLine("AFTER METHOD CALL");
Console.WriteLine("test.i={0}", test.i);
}
}
C# Classes Member Functions
using System;
public class MemberFunctions
{
public static void Main()
{
Point myPoint = new Point(10, 15);
Console.WriteLine("myPoint.X {0}", myPoint.GetX());
Console.WriteLine("myPoint.Y {0}", myPoint.GetY());
}
}
class Point
{
public Point(int x, int y)
{
this.x = x;
this.y = y;
}
// accessor functions
public int GetX() {return(x);}
public int GetY() {return(y);}
// variables now private
int x;
int y;
}
Overloading Classes
/*
* C# Programmers Pocket Consultant
* Author: Gregory S. MacBeth
* Email: gmacbeth@comporium.net
* Create Date: June 27, 2003
* Last Modified Date:
*/
using System;
namespace Client.Chapter_5___Building_Your_Own_Classes
{
public class OverloadingClasses
{
static void Main(string[] args)
{
A MyA = new A();
MyA.Display();
MyA.Display(10);
}
}
class A
{
public void Display()
{
Console.WriteLine("No Params Display Method");
}
public void Display(int A)
{
Console.WriteLine("Overloaded Display {0}", A);
}
}
}
A simple example of recursion
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
// A simple example of recursion.
using System;
class Factorial {
// This is a recursive function.
public int factR(int n) {
int result;
if(n==1) return 1;
result = factR(n-1) * n;
return result;
}
// This is an iterative equivalent.
public int factI(int n) {
int t, result;
result = 1;
for(t=1; t <= n; t++) result *= t;
return result;
}
}
public class Recursion {
public static void Main() {
Factorial f = new Factorial();
Console.WriteLine("Factorials using recursive method.");
Console.WriteLine("Factorial of 3 is " + f.factR(3));
Console.WriteLine("Factorial of 4 is " + f.factR(4));
Console.WriteLine("Factorial of 5 is " + f.factR(5));
Console.WriteLine();
Console.WriteLine("Factorials using iterative method.");
Console.WriteLine("Factorial of 3 is " + f.factI(3));
Console.WriteLine("Factorial of 4 is " + f.factI(4));
Console.WriteLine("Factorial of 5 is " + f.factI(5));
}
}
[/csharp]
Automatic type conversions can affect overloaded method resolution
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
/* Automatic type conversions can affect
overloaded method resolution. */
using System;
class Overload2 {
public void f(int x) {
Console.WriteLine("Inside f(int): " + x);
}
public void f(double x) {
Console.WriteLine("Inside f(double): " + x);
}
}
public class TypeConv {
public static void Main() {
Overload2 ob = new Overload2();
int i = 10;
double d = 10.1;
byte b = 99;
short s = 10;
float f = 11.5F;
ob.f(i); // calls ob.f(int)
ob.f(d); // calls ob.f(double)
ob.f(b); // calls ob.f(int) -- type conversion
ob.f(s); // calls ob.f(int) -- type conversion
ob.f(f); // calls ob.f(double) -- type conversion
}
}