C# SortedList

In C#, SortedList is a collection of key-value pairs sorted according to keys. By default, this collection sorts in ascending order. It is of both generic and non-generic type of collection. The generic SortedList is defined in the System.Collections.Generic namespace whereas non-generic SortedList is defined under System.Collections namespace, here we will discuss the non-generic type SortedList.

• Elements are sorted by key in ascending order.
• The keys are defined uniquely but we can store duplicate values.
• Offer to store data in keys and value pairs.
• No need to define the size we can add elements without giving the size like arrays.

Example:

Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three

Steps to Create SortedList

We can use the SortedList Class which provides different ways to create a Sorted list. Here, we use the SortedList Class constructor to create a sorted list. Which is used to create an instance of the SortedList class that is empty by default and sorted according to the IComparable interface implemented by each key added to the SortedList object.

Step 1: Include System.Collections namespace

using System.Collections;

Step 2: Create a SortedList using the SortedList class

SortedList list_name = new SortedList();

Performing Different Operations on SortedList

1. Adding Elements

For adding elements list, The SortedList class provides the following methods:

• Add() : This method is used to add an object to the SortedList<T>. 
• Collection Initializer: We can use Collection Initializer to add elements in SortedList<TKey, TValue>.

Syntax:

// Add element using Add method
list.Add(key, value);

// Adding elements using the 
// Collection initializers 
SortedList<TKey, TValue> mySortedList = new SortedList<int, string>()

{
{ key, value },
{ key, value },
};

Example: Creating sortedList using different ways.

1.02 and This
1.04 and SortedList
1.07 and Is

b.01 and 405
b.09 and 234
b.11 and 395
b.67 and 100

2. Accessing SortedList

There are three different ways to access the elements of the SortedList as it is stored in the Key-Value pair we can get the Key and value separately.

Using for Loop: We can use Loop to iterate through the list and access key-value pairs we can use List.GetKey() method to access the key and similarly from the key we can access the value by using List.GetByIndex(key).

Syntax:

for (int i = 0; i < sList.Count; i++)

{
Console.WriteLine("{0} and {1}",
sList.GetKey(i), // Accessing keys
sList.GetByIndex(i)); // Accessing values
}

Using ForEach Loop: We can use a foreach loop to access the key-value pairs of the SortedList. In the foreach loop, we can use a dictionary. It is mostly used to access the list stored in key-value pairs.

Syntax:

foreach(DictionaryEntry pair in my_slist1)
{
Console.WriteLine("{0} and {1}",
pair.Key, pair.Value);
}

Using Indexers: We can access the individual value of the SortedList by using the index. We need to pass the key or index as a parameter to find the respective value. It is similar to how we access the array.

Syntax:

Console.WriteLine("Value is:{0}", my_slist1[1.04]);
string x = (string)my_slist[1.02];
Console.WriteLine(x);

Note: If the specified key is not available, then the a runtime exception will be thrown (KeyNotFoundException).

Example: Demonstration of accessing SortedList in different ways.

Access using for loop
1: Geek1
2: Geek2
3: Geek3
Access using foreach loop
1: Geek1
2: Geek2
3: Geek3
Access using indexer
Key 2: Geek2

3. Removing Elements

• Clear: This method is used to remove all elements from a SortedList object.
• Remove: This method is used to remove the element with the specified key from a SortedList object.
• RemoveAt: This method is used to remove the element at the specified index of a SortedList object.

Example:

1 and one
2 and two
3 and three

2 and two
3 and three

2 and two

Total pairs present in sorted list is: 0

4. Check Element

We can check the element of the SortedList by using the methods available below it returns value in boolean if the the element present returns true either false.

• Contains: This method is used to check whether a SortedList object contains a specific key.
• ContainsKey: This method is used to check whether a SortedList object contains a specific key.
• ContainsValue: This method is used to check whether a SortedList object contains a specific value.

Example:

Key is found...!!
Key is found...!!
Value is found...!!

Important Points

• SortedList implements interfaces like IEnumerable, ICollection, IDictionary, and ICloneable, and elements can be accessed using both key and index.
• It internally uses two arrays (keys and values), where keys cannot be null, must be unique, and of the same type, while values can be null and can be of same or different types (in non-generic version). er exception.
• The capacity defines how many key-value pairs it can hold, and key/value pairs can also be cast to DictionaryEntry.
• We can also cast key/value pair of SortedList into DictionaryEntry.