C# | Remove all elements from a SortedList

SortedList class is a collection of (key, value) pairs which are sorted according to keys. Those pairs can be accessible by key and as well as by index(zero-based indexing). This comes under System.Collections namespace. SortedList.Clear method is used to remove all the elements from a SortedList object.

Properties:

• A SortedList element can be accessed by its key or by its index.
• A SortedList object internally maintains two arrays to store the elements of the list, i.e, one array for the keys and another array for the associated values.
• A key cannot be null, but a value can be.
• The capacity of a SortedList object is the number of elements the SortedList can hold.
• A SortedList does not allow duplicate keys.
• Operations on a SortedList object tend to be slower than operations on a Hashtable object because of the sorting.
• Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

Syntax :

public virtual void Clear ();

Exceptions:

• NotSupportedException : If the SortedList object is read-only or has a fixed size.

Example:

// C# code to remove all
// elements from a SortedList
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an SortedList
        SortedList mySortedList = new SortedList();

        // Adding elements to SortedList
        mySortedList.Add("1", "1st");
        mySortedList.Add("2", "2nd");
        mySortedList.Add("3", "3rd");
        mySortedList.Add("4", "4th");
        mySortedList.Add("5", "5th");
        mySortedList.Add("6", "6th");
        mySortedList.Add("7", "7th");

        // Displaying number of elements
        Console.WriteLine("Number of elements in SortedList is : "
                                            + mySortedList.Count);

        // Displaying capacity
        Console.WriteLine("capacity of SortedList is : "
                               + mySortedList.Capacity);

        // Removing all elements from SortedList
        mySortedList.Clear();

        // Displaying number of elements
        Console.WriteLine("Number of elements in SortedList is : "
                                            + mySortedList.Count);

        // Displaying capacity
        Console.WriteLine("capacity of SortedList is : "
                               + mySortedList.Capacity);
    }
}

Output:

Number of elements in SortedList is : 7
capacity of SortedList is : 16
Number of elements in SortedList is : 0
capacity of SortedList is : 16

Note:

• This method is an O(n) operation, where n is Count.
• Count is set to zero and references to other objects from elements of the collection are also released.
• Capacity remains unchanged. To reset the capacity of the SortedList object, call TrimToSize or set the Capacity property directly.
• Trimming an empty SortedList sets the capacity of the SortedList to the default capacity.

Reference:

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