Csharp/C Sharp/Class Interface/Class Variables

A Simple Class and Objects

<source lang="csharp">

public class Product {

   public string make;
   public string model;
   public string color;
   public int yearBuilt;
   public void Start() {
       System.Console.WriteLine(model + " started");
   }
   public void Stop() {
       System.Console.WriteLine(model + " stopped");
   }

}

class MainClass{

   public static void Main() {
       Product myProduct;
       myProduct = new Product();
       myProduct.make = "Toyota";
       myProduct.model = "MR2";
       myProduct.color = "black";
       myProduct.yearBuilt = 1995;
       System.Console.WriteLine("myProduct details:");
       System.Console.WriteLine("myProduct.make = " + myProduct.make);
       System.Console.WriteLine("myProduct.model = " + myProduct.model);
       System.Console.WriteLine("myProduct.color = " + myProduct.color);
       System.Console.WriteLine("myProduct.yearBuilt = " + myProduct.yearBuilt);
       myProduct.Start();
       myProduct.Stop();
       Product redPorsche = new Product();
       redPorsche.make = "Porsche";
       redPorsche.model = "Boxster";
       redPorsche.color = "red";
       redPorsche.yearBuilt = 2000;
       System.Console.WriteLine(          "redPorsche is a " + redPorsche.model);
       System.Console.WriteLine("Assigning redPorsche to myProduct");
       myProduct = redPorsche;
       System.Console.WriteLine("myProduct details:");
       System.Console.WriteLine("myProduct.make = " + myProduct.make);
       System.Console.WriteLine("myProduct.model = " + myProduct.model);
       System.Console.WriteLine("myProduct.color = " + myProduct.color);
       System.Console.WriteLine("myProduct.yearBuilt = " + myProduct.yearBuilt);
   }

}

</source>

Class variables with default value

<source lang="csharp"> /* Learning C# by Jesse Liberty Publisher: O"Reilly ISBN: 0596003765

• /

using System;
public class MyTimeWithDefaultValue
{
    // private member variables
    int year;
    int month;
    int date;
    int hour;
    int minute;
    int second = 30;
    // public method
    public void DisplayCurrentMyTimeWithDefaultValue()
    {
        System.Console.WriteLine("{0}/{1}/{2} {3}:{4}:{5}",
            month, date, year, hour, minute, second);
    }
    // constructor
    public MyTimeWithDefaultValue(int theYear, int theMonth, int theDate,
        int theHour, int theMinute)
    {
        year = theYear;
        month = theMonth;
        date = theDate;
        hour = theHour;
        minute = theMinute;
    }
}
public class Tester
{
    static void Main()
    {
        MyTimeWithDefaultValue timeObject = new MyTimeWithDefaultValue(2005,3,25,9,35);
        timeObject.DisplayCurrentMyTimeWithDefaultValue();
    }
}
          
      </source>

declare a class Address containing the data members to describe a US address along with the member functions

<source lang="csharp">

using System; class MainClass {

   public static void Main(string[] args) {
       Address addr = new Address();
       addr.SetStreet(123, "My Street");
       addr.SetCity("A", "X", 123456);
       Console.WriteLine(addr.GetStreetString());
       Console.WriteLine(addr.GetCityString());
       addr.Output();
   }

} class Address {

   public int nAddressNumberPart;
   public string sAddressNamePart;
   public string sCity;
   public string sState;
   public int nPostalCode;
   public void SetStreet(int nNumber, string sName) {
       nAddressNumberPart = nNumber;
       sAddressNamePart = sName;
   }
   public string GetStreetString() {
       return nAddressNumberPart + " " + sAddressNamePart;
   }
   public void SetCity(string sCityIn, string sStateIn, int nPostalCodeIn) {
       sCity = sCityIn;
       sState = sStateIn;
       nPostalCode = nPostalCodeIn;
   }
   public string GetCityString() {
       return sCity + ", " + sState + " " + nPostalCode;
   }
   public string GetAddressString() {
       return GetStreetString() + "\n" + GetCityString();
   }
   public void Output() {
       Console.WriteLine(GetAddressString());
   }

}

</source>

Default Values of Class Member Variables

<source lang="csharp"> /*

   * bool types are set to false.
   * Numeric data is set to 0 (or 0.0 in the case of floating-point data types).
   * string types are set to null.
   * char types are set to "\0".
   * Reference types are set to null.

Given these rules, ponder the following code:

• /

class Test {

    public int myInt;        // Set to 0. 
    public string myString;  // Set to null. 
    public bool myBool;      // Set to false. 
    public object myObj;     // Set to null. 

}

</source>

Field Attributes

<source lang="csharp"> 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);
               }
           }
       }
   }

}

</source>

Static class variable

<source lang="csharp"> /* Learning C# by Jesse Liberty Publisher: O"Reilly ISBN: 0596003765

• /

using System;
namespace Test_Console_App_3
{
    // declare a Cat class
    // stripped down
    class Cat
    {
        // a private static member to keep
        // track of how many Cat objects have
        // been created
        private static int instances = 0;
        private int weight;
        private String name;
        // cat constructor
        // increments the count of Cats
        public Cat(String name, int weight)
        {
            instances++;
            this.name = name;
            this.weight = weight;
        }
        // Static method to retrieve
        // the current number of Cats
        public static void HowManyCats()
        {
            Console.WriteLine("{0} cats adopted",
                instances);
        }
        public void TellWeight()
        {
            Console.WriteLine("{0} is {1} pounds",
                name, weight);
        }
    }
   public class StaticInClassTester
   {
      public void Run()
      {
          Cat.HowManyCats();
          Cat frisky = new Cat("Frisky", 5);
          frisky.TellWeight();
          Cat.HowManyCats();
          Cat whiskers = new Cat("Whisky", 7);
          whiskers.TellWeight();
          Cat.HowManyCats();
      }
      static void Main()
      {
         StaticInClassTester t = new StaticInClassTester();
         t.Run();
      }
   }
}
          
      </source>

The super-string class.

<source lang="csharp"> 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));
   }

}

</source>