ARTICLE

Hashtable in C#

Posted by Mahesh Chand in Articles | How do I on November 14, 2005

Tags: Adding Items to a Hashtable, C# Hashtable, csharp hashtable, GetEnumerator(), hash table, IDictionaryEnumerator

Hashtable is useful when you need to store data in a key and value pair. This article shows how to use hashtable in C#.

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Reader Level: Beginner

This quick how do I shows how to use a Hashtable in C#.

Creating a Hashtable

The Hashtable class in C# represents a hashtable. The following code creates a Hashtable:

private Hashtable hshTable = new Hashtable();

Adding Items to a Hashtable

Add method of Hashtable is used to add items to the hashtable. The method has index and value parameters. The following code adds three items to hashtable.

hshTable .Add("Author1", "Mahesh Chand");
hshTable .Add("Author2", "James Brand");
hshTable .Add("Author3", "Mike Gold");

Retrieving an Item Value from Hashtable

The following code returns the value of "Author1" key:

string name = hshTable["Author1"].ToString();

Removing Items from a Hashtable

The Remove method removes an item from a Hashtable. The following code removes item with index "Author1" from the hashtable:

hshTable.Remove("Author1");

Looking through all Items of a Hashtable

The following code loops through all items of a hashtable and reads the values.

// Loop through all items of a Hashtable
IDictionaryEnumerator en = hshTable.GetEnumerator();
while (en.MoveNext())
{
string str = en.Value.ToString();
}

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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace indexingform
{
    public partial class Form1 : Form
    {


        public Form1()
        {
            InitializeComponent();
        }

        Hashtable hs = new Hashtable();
        indexing.student obj;

        private void Form1_Load(object sender, EventArgs e)
        {
            obj = new indexing.student();

        }

        private void button1_Click(object sender, EventArgs e)
        {
            obj.rollno = Int32.Parse(textBox1.Text);
            obj.stuname = textBox2.Text;
            obj.age = Int32.Parse(textBox3.Text);
            hs.Add(obj.rollno,obj);


        }

        private void button7_Click(object sender, EventArgs e)
        {
            MessageBox.Show("total record=" + hs.Count.ToString());
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (hs.Count > 0)
            {
               obj.rollno= 1;
                indexing.student oo = (indexing.student)hs[obj.rollno];
                //textBox1.Text = oo.rollno.ToString();
                textBox2.Text = oo.stuname;
                textBox3.Text = oo.age.ToString();
            }
            else
            {
                MessageBox.Show("record not found");
            }

        }
    }
}
i have a problem in the bold and under line code its a nevigation botton codeing searching for the first enterd vale

Posted by praveen gaur on Jul 07, 2010

Hi mahesh, thank you for the article.
I was wondering if i can involve multiple values in the hashtable item.

Example, suppose i have an item as:
hshTable .Add("imageModify", "C:\execute.cs","inputFileLocation","outputFileLocation");

When i enter imageModify and Invoke it then the execute.cs will need to recognise imageModify and the fileLocations should be sent so that exexute.cs recognises which is the image to be modified and where it needs to be saved after executing the function in the cs file. Can i do this using Hashtables or is there some other method for this???