C# Hashtable Example

The HashTable is related to System.Collections namespace. The HashTable contains on key-value pairs. Where each key is associated with a unique value.

Features with hashtable in C#:

• Creating a HashTable:

  You will use System.Collections namespace for creating The hashtable. The below code is syntax of creating the hashtable.

  Example

  Copy Code

  using System.Collections;

  Hashtable fruittable = new Hashtable();

  using System.Collections;

  Hashtable fruittable = new Hashtable();

• Adding Key-Value Pairs:

  A HashTable contains the key-value pairs and for making key-value pairs you can use Add method. The key must be unique in each key-value pairs in Add method.

  Example

  Copy Code

  fruittable.Add("FruitName", "Apple");

  fruittable.Add("FruitPrice", 20);

  fruittable.Add("FruitColor", "Red");

  fruittable.Add("FruitName", "Apple");

  fruittable.Add("FruitPrice", 20);

  fruittable.Add("FruitColor", "Red");

• Accessing Values:

  You can retrieve values by their associated keys:

  Example

  Copy Code

  string fruitname = (string)fruittable["FruitName"];

  int fruitprice = (int)fruittable["FruitPrice"];

  string fruitcolor = (string)fruittable["FruitColor"];

  string fruitname = (string)fruittable["FruitName"];

  int fruitprice = (int)fruittable["FruitPrice"];

  string fruitcolor = (string)fruittable["FruitColor"];

• Removing Key-Value Pairs:

  You can remove key-value pairs by their key:

  Example

  Copy Code

  fruittable.Remove("FruitPrice");

  fruittable.Remove("FruitPrice");

• Checking for Existence:

  You can check if a key exists in the HashTable using the Contains method:

  Example

  Copy Code

  // Returns false after removing "FruitPrice";

  bool containsPrice = fruittable.Contains("FruitPrice");

  // Returns false after removing "FruitPrice";

  bool containsPrice = fruittable.Contains("FruitPrice");

• Iterating through a HashTable:

  You can use the DictionaryEntry structure to iterate through the key-value pairs:

  Example

  Copy Code

  foreach (DictionaryEntry entry in fruittable)

  {

  Console.WriteLine($"{entry.Key}: {entry.Value}");

  }

  foreach (DictionaryEntry entry in fruittable)

  {

  Console.WriteLine($"{entry.Key}: {entry.Value}");

  }

• Other HashTable Operations:

  The HashTable class also provides methods and properties for checking the number of key-value pairs, clearing the HashTable, and more.

  Example

  Copy Code

  int count = hashtable.Count;

  // Removes all key-value pairs

  hashtable.Clear();

  int count = hashtable.Count;

  // Removes all key-value pairs

  hashtable.Clear();

• HashTable in C# with Example

  Copy Code

  using System;

  using System.Collections;

  public class CSharpProgram

  {

  public static void Main(string[] arge)

  {

  Hashtable fruittable = new Hashtable();

  fruittable.Add("FruitName", "Apple");

  fruittable.Add("FruitPrice", 20);

  fruittable.Add("FruitColor", "Red");

  foreach (DictionaryEntry entry in fruittable)

  {

  Console.WriteLine($"{entry.Key}: {entry.Value}");

  }

  fruittable.Remove("FruitPrice");

  foreach (DictionaryEntry entry in fruittable)

  {

  Console.WriteLine($"{entry.Key}: {entry.Value}");

  }

  }

  }

  using System;

  using System.Collections;

  public class CSharpProgram

  {

  public static void Main(string[] arge)

  {

  Hashtable fruittable = new Hashtable();

  fruittable.Add("FruitName", "Apple");

  fruittable.Add("FruitPrice", 20);

  fruittable.Add("FruitColor", "Red");

  foreach (DictionaryEntry entry in fruittable)

  {

  Console.WriteLine($"{entry.Key}: {entry.Value}");

  }

  fruittable.Remove("FruitPrice");

  foreach (DictionaryEntry entry in fruittable)

  {

  Console.WriteLine($"{entry.Key}: {entry.Value}");

  }

  }

  }

  
  
  

  Output

  FruitName: Apple

  FruitColor: Red

  FruitPrice: 20

  FruitName: Apple

  FruitColor: Red

Summary

HashTable is collection of Key-Value pairs. In Key-Value pairs, each key must be unique. HashTable can store any type (int, float, string, bool) of data.