Csharp/CSharp Tutorial/Data Structure/ArrayList object

Add object with IComparable interface implementation to an ArrayList

using System; 
using System.Collections; 
 
// Implement the non-generic IComparable interface. 
class Product : IComparable { 
  string name; 
  double cost; 
  int onhand; 
 
  public Product(string n, double c, int h) { 
    name = n; 
    cost = c; 
    onhand = h; 
  } 
 
  public override string ToString() { 
    return 
      String.Format("{0,-10}Cost: {1,6:C}  On hand: {2}", 
                    name, cost, onhand); 
  } 
 
  // Implement the IComparable interface. 
  public int CompareTo(object obj) { 
    Product b; 
    b = (Product) obj; 
    return name.rupareTo(b.name); 
  } 
} 
 
class MainClass { 
  public static void Main() { 
    ArrayList inv = new ArrayList(); 
     
    // Add elements to the list 
    inv.Add(new Product("A", 5.5, 3)); 
    inv.Add(new Product("B", 8.9, 2));    
    inv.Add(new Product("C", 3.0, 4)); 
    inv.Add(new Product("D", 1.8, 8)); 
 
    Console.WriteLine("Product list before sorting:"); 
    foreach(Product i in inv) { 
      Console.WriteLine("   " + i); 
    } 
    Console.WriteLine(); 
 
    // Sort the list. 
    inv.Sort(); 
 
    Console.WriteLine("Product list after sorting:"); 
    foreach(Product i in inv) { 
      Console.WriteLine("   " + i); 
    } 
  } 
}

Product list before sorting:
   A         Cost:  $5.50  On hand: 3
   B         Cost:  $8.90  On hand: 2
   C         Cost:  $3.00  On hand: 4
   D         Cost:  $1.80  On hand: 8
Product list after sorting:
   A         Cost:  $5.50  On hand: 3
   B         Cost:  $8.90  On hand: 2
   C         Cost:  $3.00  On hand: 4
   D         Cost:  $1.80  On hand: 8

Add reference objects to ArrayList

using System;
using System.Collections;
using System.Collections.Specialized;
class MyClass{
   public string MyName="";   
}
class MainClass
{
  static void Main(string[] args)
  {
    ArrayList classList = new ArrayList();
    classList.AddRange(new MyClass[] { new MyClass(), 
                                           new MyClass(), 
                                           new MyClass()});
    Console.WriteLine("Items in List: {0}", classList.Count);
    // Print out current values. 
    foreach(MyClass c in classList)
    {
      Console.WriteLine("MyClass name: {0}", c.MyName);  
    }
  }
}

Items in List: 3
MyClass name:
MyClass name:
MyClass name:

Add user-defined object to an ArrayList

using System; 
using System.Collections; 
 
class Product { 
  string name; 
  double cost; 
  int onhand; 
 
  public Product(string n, double c, int h) { 
    name = n; 
    cost = c; 
    onhand = h; 
  } 
 
  public override string ToString() { 
    return 
      String.Format("{0,-10}Cost: {1,6:C}  On hand: {2}", 
                    name, cost, onhand); 
  } 
} 
 
class MainClass { 
  public static void Main() { 
    ArrayList inv = new ArrayList(); 
     
    // Add elements to the list 
    inv.Add(new Product("A", 5.9, 3)); 
    inv.Add(new Product("B", 8.2, 2));    
    inv.Add(new Product("C", 3.5, 4)); 
    inv.Add(new Product("D", 1.8, 8)); 
 
    Console.WriteLine("Product list:"); 
    foreach(Product i in inv) { 
      Console.WriteLine("   " + i); 
    } 
  } 
}

Product list:
   A         Cost:  $5.90  On hand: 3
   B         Cost:  $8.20  On hand: 2
   C         Cost:  $3.50  On hand: 4
   D         Cost:  $1.80  On hand: 8

ArrayList and your own object: Add objects to ArrayList

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}

class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979

ArrayList and your own object: Get an enumerator using the GetEnumerator() method and use it to read the object elements in ArrayList

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}
class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    IEnumerator myEnumerator = myArrayList.GetEnumerator();
    while (myEnumerator.MoveNext())
    {
      Console.WriteLine("myEnumerator.Current = " + myEnumerator.Current);
    }
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
myEnumerator.Current = Name is M, Number is 2001
myEnumerator.Current = Name is B, Number is 2001
myEnumerator.Current = Name is C, Number is 1999
myEnumerator.Current = Name is T, Number is 1979

ArrayList and your own object: remove an object from ArrayList

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}
class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    myArrayList.Remove(myB);
    DisplayArrayList("myArrayList", myArrayList);
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is C, Number is 1999
myArrayList[2] = Name is T, Number is 1979

ArrayList and your own object: Use the BinarySearch() method to search myArrayList for an object

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}
class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    myArrayList.Sort();
    DisplayArrayList("myArrayList", myArrayList);
    int index2 = myArrayList.BinarySearch(myC);
    Console.WriteLine("Found myC at index " + index2);
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
myArrayList[0] = Name is T, Number is 1979
myArrayList[1] = Name is C, Number is 1999
myArrayList[2] = Name is M, Number is 2001
myArrayList[3] = Name is B, Number is 2001
Found myC at index 1

ArrayList and your own object: Use the Contains() method to determine if an object is in the ArrayList

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}

class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    if (myArrayList.Contains(myB))
    {
      Console.WriteLine("myArrayList does contain myB");
      int index = myArrayList.IndexOf(myB);
      Console.WriteLine("myB occurs at index " + index);
    }
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
myArrayList does contain myB
myB occurs at index 1

ArrayList and your own object: Use the GetRange() method to get a range of object elements from ArrayList

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}
class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    ArrayList anotherArrayList = myArrayList.GetRange(1, 2);
    DisplayArrayList("anotherArrayList", anotherArrayList);
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
anotherArrayList[0] = Name is B, Number is 2001
anotherArrayList[1] = Name is C, Number is 1999

ArrayList and your own object: use the IndexOf() method to display the index of an object

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}

class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    if (myArrayList.Contains(myB))
    {
      Console.WriteLine("myArrayList does contain myB");
      int index = myArrayList.IndexOf(myB);
      Console.WriteLine("myB occurs at index " + index);
    }
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
myArrayList does contain myB
myB occurs at index 1

ArrayList and your own object: Use the Sort() method to sort objects in the ArrayList

using System;
using System.Collections;
class Employee : IComparable
{
  public string Name;
  public int Number;
  public Employee(string Name, int Number)
  {
    this.Name = Name;
    this.Number = Number;
  }
  public override string ToString()
  {
    return "Name is " + Name + ", Number is " + Number;
  }
  public int Compare(object lhs, object rhs)
  {
    Employee lhsEmployee = (Employee) lhs;
    Employee rhsEmployee = (Employee) rhs;
    if (lhsEmployee.Number < rhsEmployee.Number) {
      return -1;
    } else if (lhsEmployee.Number > rhsEmployee.Number) {
      return 1;
    } else {
      return 0;
    }
  }
  public int CompareTo(object rhs) {
    return Compare(this, rhs);
  }
}
class MainClass
{
  public static void DisplayArrayList(string arrayListName, ArrayList myArrayList) {
    for (int i = 0; i < myArrayList.Count; i++) {
      Console.WriteLine(arrayListName + "[" + i + "] = " + myArrayList[i]);
    }
  }
  public static void Main()
  {
    ArrayList myArrayList = new ArrayList();
    // add four Employee objects to myArrayList using the Add() method
    Console.WriteLine("Adding four Employee objects to myArrayList");
    Employee myM = new Employee("M", 2001);
    Employee myB = new Employee("B", 2001);
    Employee myC = new Employee("C", 1999);
    Employee myT = new Employee("T", 1979);
    myArrayList.Add(myM);
    myArrayList.Add(myB);
    myArrayList.Add(myC);
    myArrayList.Add(myT);
    DisplayArrayList("myArrayList", myArrayList);
    myArrayList.Sort();
    DisplayArrayList("myArrayList", myArrayList);
  }
}

Adding four Employee objects to myArrayList
myArrayList[0] = Name is M, Number is 2001
myArrayList[1] = Name is B, Number is 2001
myArrayList[2] = Name is C, Number is 1999
myArrayList[3] = Name is T, Number is 1979
myArrayList[0] = Name is T, Number is 1979
myArrayList[1] = Name is C, Number is 1999
myArrayList[2] = Name is M, Number is 2001
myArrayList[3] = Name is B, Number is 2001