C# | Getting a subset of the elements from the source ArrayList

ArrayList.GetRange(Int32, Int32) Method is used to get an ArrayList which will represent a subset of the elements in the source ArrayList.

Syntax:

public virtual System.Collections.ArrayList GetRange (int index, int count);

Parameters:

index: It is of Int32 type and represents the zero-based ArrayList index at which the range starts.
count: It is of Int32 type and represents the number of elements in the range.

Return Value: This method returns an ArrayList which represents a subset of the elements in the source ArrayList.

Exceptions:

• ArgumentOutOfRangeException: If the value of the index is less than zero, or if the value of count is less than zero.
• ArgumentException: If the value of an index and count does not denote a valid range of elements in the ArrayList.

Below programs illustrate the above-discussed method:

Example 1:

// C# program to illustrate the
// concept of GetRange() Method
using System;
using System.Collections;

class GFG {

    // Main method
    public static void Main()
    {

        // Creates and initializes
        // a new ArrayList.
        ArrayList myarraylist = new ArrayList();
        myarraylist.Add("Welcome");
        myarraylist.Add("to");
        myarraylist.Add("Geeks");
        myarraylist.Add("for");
        myarraylist.Add("Geeks");
        myarraylist.Add("portal");

        // Creates and initializes queue
        Queue mynewList = new Queue();
        mynewList.Enqueue("This");
        mynewList.Enqueue("is");
        mynewList.Enqueue("C#");
        mynewList.Enqueue("tutorial");

        // Displays the values of six
        // elements starting at index 0.
        ArrayList newarraylist = myarraylist.GetRange(0, 6);
        Console.WriteLine("Elements are:");
        Displaydata(newarraylist, '\n');

        // Replaces the values of six elements
        // starting at index 1 with the values
        // in the queue.
        myarraylist.SetRange(2, mynewList);

        // Displays the values of six
        // elements starting at index 0.
        newarraylist = myarraylist.GetRange(0, 6);
        Console.WriteLine("\nNow elements are:");
        Displaydata(newarraylist, '\n');
    }

    public static void Displaydata(IEnumerable myvalueList,
                                          char mySeparator)
    {
        foreach(Object obj in myvalueList)
            Console.Write("{0}{1}", mySeparator, obj);
        Console.WriteLine();
    }
}

Output:

Elements are:

Welcome
to
Geeks
for
Geeks
portal

Now elements are:

Welcome
to
This
is
C#
tutorial

Example 2:

// C# program to illustrate the
// concept of GetRange() Method
using System;
using System.Collections;

class GFG {

    // Main method
    public static void Main()
    {

        // Creates and initializes a new ArrayList.
        ArrayList myarraylist = new ArrayList();
        myarraylist.Add("Welcome");
        myarraylist.Add("to");
        myarraylist.Add("Geeks");
        myarraylist.Add("for");
        myarraylist.Add("Geeks");
        myarraylist.Add("portal");

        // Creates and initializes queue
        Queue mynewList = new Queue();
        mynewList.Enqueue("This");
        mynewList.Enqueue("is");
        mynewList.Enqueue("C#");
        mynewList.Enqueue("tutorial");

        // Displays the values of six elements
        ArrayList newarraylist = myarraylist.GetRange(-1, 6);
        Console.WriteLine("Elements are:");
        Displaydata(newarraylist, '\n');

        // Replaces the values of six elements
        // starting at index 1 with the
        // values in the queue.
        myarraylist.SetRange(2, mynewList);

        // Displays the values of six
        // elements starting at index 0.
        newarraylist = myarraylist.GetRange(0, 6);
        Console.WriteLine("Now elements are:");
        Displaydata(newarraylist, '\n');
    }

    public static void Displaydata(IEnumerable myvalueList,
                                          char mySeparator)
    {
        foreach(Object obj in myvalueList)
            Console.Write("{0}{1}", mySeparator, obj);
        Console.WriteLine();
    }
}

Runtime Error:

Unhandled Exception:
System.ArgumentOutOfRangeException: Non-negative number required.
Parameter name: index

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.arraylist.getrange?view=netframework-4.7.2#System_Collections_ArrayList_GetRange_System_Int32_System_Int32_