How to check the availability of key/value pair in hashtable?
In hashtable, you can check whether the given pair is present or not using the following methods:
- Contains: This method is used to check whether the Hashtable contains a specific key.
- ContainsKey: This method is also used to check whether the Hashtable contains a specific key.
- ContainsValue: This method is used to check whether the Hashtable contains a specific value.
Example:
C#
// C# program to illustrate how// to check key/value present// in the hashtable or notusing System;using System.Collections;class GFG { // Main Method static public void Main() { // Create a hashtable // Using Hashtable class Hashtable my_hashtable = new Hashtable(); // Adding key/value pair in the hashtable // Using Add() method my_hashtable.Add("A1", "Welcome"); my_hashtable.Add("A2", "to"); my_hashtable.Add("A3", "w3wiki"); // Determine whether the given // key present or not // using Contains method Console.WriteLine(my_hashtable.Contains("A3")); Console.WriteLine(my_hashtable.Contains(12)); Console.WriteLine(); // Determine whether the given // key present or not // using ContainsKey method Console.WriteLine(my_hashtable.ContainsKey("A1")); Console.WriteLine(my_hashtable.ContainsKey(1)); Console.WriteLine(); // Determine whether the given // value present or not // using ContainsValue method Console.WriteLine(my_hashtable.ContainsValue("geeks")); Console.WriteLine(my_hashtable.ContainsValue("to")); }} |
Output
True False True False False True
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.
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