C# | ArrayList whose elements are copies of the specified value

ArrayList.Repeat(Object, Int32) Method is used to return an ArrayList whose elements are copies of the specified value. Or in other words, this method is used when you want to repeat a specified element in the ArrayList. This method is an O(n) operation, where n is the number of times item should be copied.

Syntax:

public static ArrayList Repeat (object item, int count);

Parameters:

item: It is an Object to copy multiple times in the new ArrayList. The value can be null.
count: It counts the number of times item should be copied.

Return Value: This method returns an ArrayList with a count number of elements, all of which are copies of the item.

Exception: If the value of count is less than zero then this method will give ArgumentOutOfRangeException.

Below given are some examples to understand the implementation in a better way:

Example 1:

// C# program to illustrate the use of
// ArrayList.Repeat(Object, Int32) Method
using System;
using System.Collections;

class GFG {

    // Main method
    public static void Main()
    {

        // Create and repeat the element
        // of ArrayList "mylist"
        ArrayList mylist = ArrayList.Repeat("GFG", 6);

        // Display element
        foreach(Object ob in mylist)
        {
            Console.WriteLine(ob);
        }

        // Display and count the total number of element
        Console.WriteLine("The count of the item is : {0}", mylist.Count);
    }
}

Output:

GFG
GFG
GFG
GFG
GFG
GFG
The count of the item is : 6

Example 2:

// C# program to illustrate the use of
// ArrayList.Repeat(Object, Int32) Method
using System;
using System.Collections;

class GFG {

    // Main method
    public static void Main()
    {

        // Create and repeat the
        // element of mylist ArrayList
        // this will give runtime error
        // as count is less than 0
        ArrayList mylist = ArrayList.Repeat(43, -1);

        // Display element
        foreach(Object ob in mylist)
        {
            Console.WriteLine(ob);
        }

        // Display and count the total number of element
        Console.WriteLine("The count of the item is : {0}", mylist.Count);
    }
}

Runtime Error:

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

Reference:

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