How to update an Hash Table?

How to check the availability of key/value pair in hashtable?

In C#, the Hashtable class does not provide a direct method to update the value of an existing key. However, you can achieve the update by following these steps:

Check if the key exists in the Hashtable using the ContainsKey method.
If the key exists, retrieve the current value using the key and store it in a variable.
Assign the new value to the key in the Hash table using the same key.
Optionally, remove the old key/value pair if needed.

Here’s an example that demonstrates how to update a value in a Hash table:

C#

using System;
using System.Collections;
  
class Program
{
    static void Main()
    {
        // Create a new Hashtable
        Hashtable hashtable = new Hashtable();
          
        // Add some key-value pairs
        hashtable.Add("key1", "value1");
        hashtable.Add("key2", "value2");
  
        // Updating the value of an existing key
        string keyToUpdate = "key1";
        if (hashtable.ContainsKey(keyToUpdate))
        {
            hashtable[keyToUpdate] = "updatedValue";
        }
  
        // Accessing the updated value
        string updatedValue = (string)hashtable[keyToUpdate];
        Console.WriteLine("Updated value: " + updatedValue);
  
        // Print all key-value pairs in the hashtable
        foreach (DictionaryEntry entry in hashtable)
        {
            Console.WriteLine("Key: " + entry.Key + ", Value: " + entry.Value);
        }
    }
}

Output

Updated value: updatedValue
Key: key1, Value: updatedValue
Key: key2, Value: value2

C# Hashtable with Examples

A Hashtable is a collection of key/value pairs that are arranged based on the hash code of the key. In other words, a Hashtable is used to create a collection that uses a hash table for storage. It generally optimizes the lookup by calculating the hash code of every key and storing it into another basket automatically and when you access the value from the hashtable at that time it matches the hashcode with the specified key. It is the non-generic type of collection that is defined in the System. Collections namespace.

Important Points:

In Hashtable, the key cannot be null, but the value can be.
In Hashtable, key objects must be immutable as long as they are used as keys in the Hashtable.
The capacity of a Hashtable is the number of elements that Hashtable can hold.
A hash function is provided by each key object in the Hashtable.
The Hashtable class implements the IDictionary, ICollection, IEnumerable, ISerializable, IDeserializationCallback, and ICloneable interfaces.
In the hashtable, you can store elements of the same type and of the different types.
The elements of the hashtable that is a key/value pair are stored in DictionaryEntry, so you can also cast the key/value pairs to a DictionaryEntry.
that key that must be unique. Duplicate keys are not allowed.

Tags:

#CSharp-Collections-Hashtable #CSharp-Collections-Namespace #C#

How to check the availability of key/value pair in hashtable?

How to update an Hash Table?

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C# Hashtable with Examples

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