When it comes to working with collections in C#, you’ll often find yourself deciding between using a List or a Dictionary, as both serve for storing and managing data and belong to System.Collection.Generics
namespace.
In this article, we’ll discuss List vs Dictionary in C# with Examples and will understand when to use each and why.
Table of Contents
- 1 What is List in C#?
- 2 What is Dictionary in C#?
- 3 List vs Dictionary in C#
- 4 Frequently Asked Questions (FAQs)
- 4.1 Q1: What is the main difference between List and Dictionary in C#?
- 4.2 Q2: When should I use a List in C#?
- 4.3 Q3: In which scenarios should I use Dictionary in C#?
- 4.4 Q4: Is it possible to iterate through a Dictionary in C#?
- 4.5 Q5 : What are the time complexities for insertion and deletion operations in Lists and Dictionaries?
- 4.6 Related
What is List in C#?
A List in C# is a dynamic array that can hold a collection of elements of the same type. It allows you to store and manipulate a list of items, such as integers, strings, or custom objects.
Lists maintain the order of elements and are accessible using indexes.
Code Example of List:
In this example, we create a List of strings, add some names to it, and then loop through the List to print each name.
using System;
using System.Collections.Generic;
class Program
{
static void Main()
{
List<string> names = new List<string>();
names.Add("Shekh Ali");
names.Add("Selena");
names.Add("Roman");
foreach (string name in names)
{
Console.WriteLine(name);
}
Console.ReadLine();
}
}
Output:
Shekh Ali
Selena
Roman
What is Dictionary in C#?
A Dictionary in C# is used to store key-value pairs where each element is associated with a unique key.
It’s like a real dictionary where you have a word (the key) and its definition (the value). You can use the key to retrieve the associated value quickly.
A Dictionary in C# is a generic collection class available in the System.Collections.Generic
namespace.
Code Example of Dictionary:
In this C# Dictionary example, we use names as keys and ages as values. You can access the value associated with a key efficiently.
using System;
using System.Collections.Generic;
class Program
{
static void Main()
{
Dictionary<string, int> ages = new Dictionary<string, int>();
ages["Shekh Ali"] = 25;
ages["Bob"] = 30;
ages["Marry"] = 35;
Console.WriteLine("Marry's age: " + ages["Marry"]);
Console.ReadLine();
}
}
Output:
Marry's age: 35
List vs Dictionary in C#
Now, let’s delve into the differences between List and Dictionary in C#.
Aspect | List | Dictionary |
---|---|---|
Purpose: | List in C# is used for storing a collection of elements of same type. | Dictionary in C# is used for storing key-value pairs where each key is unique. |
Data Structure: | List is an ordered collection. Elements are stored in the order they were added. | Dictionary stores Key-Value pairs where elements are accessed by a unique key. |
Duplicate Values: | List allows duplicate values. | Dictionary requires unique keys. Adding a duplicate key will overwrite the existing value. |
Lookup Efficiency: | You must iterate through the list to find a specific element. This can be slow for large lists. | Dictionary Offers constant-time lookup for values based on keys. It’s lightning-fast for retrieval. |
Memory Consumption: | List uses less memory because it only stores elements. | On the other hand, Dictionary uses more memory because it stores both keys and values. |
Error Handling: | Index Out of Range: Accessing an index beyond the List’s size results in an exception. Searching can be slow for large Lists. | Key Not Found: Trying to access a key that doesn’t exist in a Dictionary throws an exception. |
Common Use Cases: | List is suitable when you need to maintain the order of elements or when duplicate values are allowed. | Dictionary is Ideal for situations where you need fast lookups based on unique keys. |
Frequently Asked Questions (FAQs)
We understand that comparing Lists and Dictionaries in C# can raise several questions.
Here, we’ve gathered some of the most common queries to provide further clarity on the topic.
Q1: What is the main difference between List and Dictionary in C#?
Lists are dynamic arrays that store a collection of objects and provide fast access by index, while Dictionaries are key-value pairs and optimized for quick access of data using keys.
Q2: When should I use a List in C#?
Q3: In which scenarios should I use Dictionary in C#?
They are ideal for scenarios where you require fast key-based lookups, such as implementing a cache, managing configuration settings, or building efficient data retrieval systems.
Q4: Is it possible to iterate through a Dictionary in C#?
foreach
loops for both keys and values.However, the order in which the elements are iterated may be different from the order in which they were added.
Q5 : What are the time complexities for insertion and deletion operations in Lists and Dictionaries?
Dictionaries, while allowing these operations, are less efficient, with an average case of O(1) and a worst-case scenario of O(n).
References: MSDN-Dictionary Class, List in C#
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