What is the HashTable in C#?

A Hashtable is a .NET class which associates a key with a value and enables you to quickly retrieve a value given its key.

Internally, it is stored as a collection of DictionaryEntry structures.

The keys and values can be of any type but the keys must be unique, immutable and not null. However, none of these restrictions apply to the values.

Here's a simple example which illustrates the use of Hashtable:

using System;

using System.Collections;

class Person

{

public string Name {get; set;}

public int Age {get;set;}

public Person(string name, int age)

{

Name = name;

Age = age;

}

public override string ToString()

{

return String.Format("Name = {0}, Age = {1}", Name, Age);

}

class Program

{

static void Main()

{

Hashtable ht = new Hashtable();

ht.Add(1, new Person("Fred", 30));

ht.Add(2, new Person("George", 40));

// retrieve Person with a key of 2

Person p = (Person)ht[2];

Console.WriteLine("Key = {0}, {1}", 2, p);

// remove person with a key of 2

ht.Remove(2);

// iterate through remaining members

foreach(DictionaryEntry de in ht)

{

Console.WriteLine("Key = {0}, {1}", de.Key, de.Value);

}

Console.ReadKey();

}

}

The output is:

Key = 2, Name = George, Age = 40

Key = 1, Name = Fred, Age = 30

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Abhishek Jaiswal12y ago
Accepted answer
HELLO
pls go through these links

http://www.c-sharpcorner.com/UploadFile/2072a9/dictionaries-and-hash-table-in-C-Sharp496/

http://msdn.microsoft.com/en-us/library/system.collections.hashtable.aspx

http://www.tutorialspoint.com/csharp/csharp_hashtable.htm

:)
Joe Wilson12y ago
Thank you very much for these suggestions.
Joe Wilson
Joe Wilson12y ago
Thank you for your attention.
Vulpes12y ago
Sure, check out this one:

http://www.dotnetperls.com/hashtable
Joe Wilson12y ago
Thank you for your answer, but if it is possible, Please Suggest Websites about the subject.
Vulpes12y ago
A Hashtable is a .NET class which associates a key with a value and enables you to quickly retrieve a value given its key.

Internally, it is stored as a collection of DictionaryEntry structures.

The keys and values can be of any type but the keys must be unique, immutable and not null. However, none of these restrictions apply to the values.

Here's a simple example which illustrates the use of Hashtable:

using System;
using System.Collections;

class Person
{
public string Name {get; set;}
public int Age {get;set;}

public Person(string name, int age)
{
Name = name;
Age = age;
}

public override string ToString()
{
return String.Format("Name = {0}, Age = {1}", Name, Age);
}
}

class Program
{
static void Main()
{
Hashtable ht = new Hashtable();
ht.Add(1, new Person("Fred", 30));
ht.Add(2, new Person("George", 40));

// retrieve Person with a key of 2
Person p = (Person)ht[2];
Console.WriteLine("Key = {0}, {1}", 2, p);

// remove person with a key of 2
ht.Remove(2);

// iterate through remaining members
foreach(DictionaryEntry de in ht)
{
Console.WriteLine("Key = {0}, {1}", de.Key, de.Value);
}

Console.ReadKey();
}
}

The output is:

Key = 2, Name = George, Age = 40
Key = 1, Name = Fred, Age = 30