C# | Remove the element with the specified key from a SortedList

Last Updated : 11 Oct, 2018

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.Remove(Object) method is used to remove the element with the specified key 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 Remove (object key);

Here, key is the key of the element to remove. Exceptions:

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

Below given are some examples to understand the implementation in a better way: Example 1:

CSHARP

// C# code to remove the element
// with the specified key 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("IN", "INDIA");
        mySortedList.Add("NY", "NEW-YORK");
        mySortedList.Add("UK", "UNITED KINGDOM");
        mySortedList.Add("GER", "GERMANY");
        mySortedList.Add("CH", "CHINA");

        // Displaying elements in SortedList
        foreach (string mykey in mySortedList.Keys)
            Console.WriteLine("Key = " + mykey);

        foreach (string myvalue in mySortedList.Values)
            Console.WriteLine("Key = " + myvalue);

        // Removing element having key as "UK"
        Console.WriteLine("Removing element having key as UK");

        mySortedList.Remove("UK");

        // Displaying elements in SortedList
        foreach (string mykey in mySortedList.Keys)
            Console.WriteLine("Key = " + mykey);

        foreach (string myvalue in mySortedList.Values)
            Console.WriteLine("Key = " + myvalue);
    }
}

Output:

Key = CH
Key = GER
Key = IN
Key = NY
Key = UK
Key = CHINA
Key = GERMANY
Key = INDIA
Key = NEW-YORK
Key = UNITED KINGDOM
Removing element having key as UK
Key = CH
Key = GER
Key = IN
Key = NY
Key = CHINA
Key = GERMANY
Key = INDIA
Key = NEW-YORK

Example 2:

CSHARP

// C# code to remove the element
// with the specified key from a SortedList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

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

        // Adding elements to SortedList
        mySortedList.Add("IN", "INDIA");
        mySortedList.Add("NY", "NEW-YORK");
        mySortedList.Add("UK", "UNITED KINGDOM");
        mySortedList.Add("GER", "GERMANY");
        mySortedList.Add("CH", "CHINA");

        // Displaying elements in SortedList
        foreach (string mykey in mySortedList.Keys)
            Console.WriteLine("Key = " + mykey);

        foreach (string myvalue in mySortedList.Values)
            Console.WriteLine("Key = " + myvalue);

        // Removing element having key as null
        Console.WriteLine("Removing element having key as null");

        // It should raise ArgumentNullException
        // as key can not be null
        mySortedList.Remove(null);

        // Displaying elements in SortedList
        foreach (string mykey in mySortedList.Keys)
            Console.WriteLine("Key = " + mykey);

        foreach (string myvalue in mySortedList.Values)
            Console.WriteLine("Key = " + myvalue);
    }
}

Error:

Unhandled Exception: System.ArgumentNullException: Key cannot be null. Parameter name: key

Note:

If the SortedList object does not contain an element with the specified key, the SortedList remains unchanged. No exception is thrown.
This method is an O(n) operation, where n is Count.

Reference:

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

C# | Remove the element with the specified key from the Hashtable

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C# | Remove the element with the specified key from a SortedList

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