Search in a SortedList object in C#

In C#, a SortedList is a collection that maintains key-value pairs sorted by keys. You can search for specific keys or values using built-in methods like ContainsKey() and ContainsValue(). The SortedList automatically keeps elements sorted, making searches efficient.

Syntax

Following are the key search methods for SortedList −

// Check if a key exists
bool ContainsKey(object key)

// Check if a value exists  
bool ContainsValue(object value)

// Get value by key (returns null if not found)
object this[object key] { get; set; }

// Get index of a key (-1 if not found)
int IndexOfKey(object key)

// Get index of a value (-1 if not found)
int IndexOfValue(object value)

Using ContainsKey() and ContainsValue()

The most common search operations check for the existence of keys or values in the SortedList −

using System;
using System.Collections;

public class Demo {
    public static void Main() {
        SortedList list = new SortedList();
        list.Add("1", "One");
        list.Add("2", "Two");
        list.Add("3", "Three");
        list.Add("4", "Four");
        list.Add("5", "Five");
        list.Add("6", "Six");
        list.Add("7", "Seven");
        list.Add("8", "Eight");
        
        Console.WriteLine("Key and Value of SortedList....");
        foreach(DictionaryEntry k in list)
            Console.WriteLine("Key: {0}, Value: {1}", k.Key, k.Value);
        
        Console.WriteLine("Is the SortedList having the value? " + list.ContainsValue("Three"));
        Console.WriteLine("The SortedList object has a fixed size? = " + list.IsFixedSize);
        Console.WriteLine("Does the SortedList object contains key 10? = " + list.ContainsKey("10"));
    }
}

The output of the above code is −

Key and Value of SortedList....
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
Key: 4, Value: Four
Key: 5, Value: Five
Key: 6, Value: Six
Key: 7, Value: Seven
Key: 8, Value: Eight
Is the SortedList having the value? True
The SortedList object has a fixed size? = False
Does the SortedList object contains key 10? = False

Using IndexOfKey() and IndexOfValue()

You can also find the index position of keys and values in the sorted collection −

using System;
using System.Collections;

public class Demo {
    public static void Main() {
        SortedList sortedList = new SortedList();
        sortedList.Add("A", "1");
        sortedList.Add("B", "2");
        sortedList.Add("C", "3");
        sortedList.Add("D", "4");
        sortedList.Add("E", "5");
        
        Console.WriteLine("SortedList elements...");
        foreach(DictionaryEntry d in sortedList) {
            Console.WriteLine("Key = " + d.Key + ", Value = " + d.Value);
        }
        
        Console.WriteLine("Count of SortedList key-value pairs = " + sortedList.Count);
        Console.WriteLine("Index of key 'C': " + sortedList.IndexOfKey("C"));
        Console.WriteLine("Index of value '4': " + sortedList.IndexOfValue("4"));
        Console.WriteLine("Index of key 'Z' (not found): " + sortedList.IndexOfKey("Z"));
        
        Console.WriteLine("Does the SortedList object contains key M? = " + sortedList.ContainsKey("M"));
        Console.WriteLine("Does the SortedList object contains key C? = " + sortedList.ContainsKey("C"));
    }
}

The output of the above code is −

SortedList elements...
Key = A, Value = 1
Key = B, Value = 2
Key = C, Value = 3
Key = D, Value = 4
Key = E, Value = 5
Count of SortedList key-value pairs = 5
Index of key 'C': 2
Index of value '4': 3
Index of key 'Z' (not found): -1
Does the SortedList object contains key M? = False
Does the SortedList object contains key C? = True

Accessing Values by Key

You can directly access values using the key as an index. If the key doesn't exist, it returns null −

using System;
using System.Collections;

public class Demo {
    public static void Main() {
        SortedList list = new SortedList();
        list.Add("apple", "fruit");
        list.Add("carrot", "vegetable");
        list.Add("banana", "fruit");
        
        Console.WriteLine("SortedList contents:");
        foreach(DictionaryEntry item in list) {
            Console.WriteLine("{0} = {1}", item.Key, item.Value);
        }
        
        Console.WriteLine("\nSearching for specific items:");
        Console.WriteLine("Value for 'apple': " + list["apple"]);
        Console.WriteLine("Value for 'carrot': " + list["carrot"]);
        Console.WriteLine("Value for 'grape' (doesn't exist): " + list["grape"]);
        
        Console.WriteLine("Contains key 'banana': " + list.ContainsKey("banana"));
        Console.WriteLine("Contains value 'vegetable': " + list.ContainsValue("vegetable"));
    }
}

The output of the above code is −

SortedList contents:
apple = fruit
banana = fruit
carrot = vegetable

Searching for specific items:
Value for 'apple': fruit
Value for 'carrot': vegetable
Value for 'grape' (doesn't exist): 
Contains key 'banana': True
Contains value 'vegetable': True

Conclusion

Searching in a SortedList is efficient and straightforward using methods like ContainsKey(), ContainsValue(), IndexOfKey(), and IndexOfValue(). The automatic sorting of elements by keys ensures consistent ordering and enables efficient search operations for large collections.