Difference Between HashTable and Dictionary in C#

Both HashTable and Dictionary stores values in form of Key-Value pairs,To access the values from Hash Table or from Dictionary we use Key to get value.But their are other difference between HashTable and Dictionary shown below.

HashTable :

• Hash table is not a generic type.
• Hashtable is a collection of data structures to hold data as key-value pairs.
• The Hashtable is a weakly typed data structure, so you can add keys and values of any Object Type to the Hashtable.
• In Hashtable boxing/unboxing (valuetypes need boxing) will happened and which may have memory consumption
• When we add values to HashTable the order of values is not maintained while retrieving.

Declarartion:

Hashtable numbers = new Hashtable();

Dictionary:

• Dictionary is a generic type.
• Dictionary is a collection of data structures to hold data as key-value pairs.
• The Dictionary is a strongly typed data structure, so you should specify the data types for both the key and value < T Key, T Value >.
• In Dictionary boxing/unboxing (valuetypes need boxing) will not happened 
• When we add values to Dictionary the order is maintained while retrieving

Declarartion:
Dictionary<int, string> dictionary = new Dictionary<int, string >();

I will explane clearly with example
Step1: Create one page in web application and design page add following code in form tag  of page
<div>
<table>
<tr>
<td>
<asp:Button ID="Button1" runat="server" Text="BindValuesToDropDown" OnClick="Button1_Click" />
</td>
</tr>
<tr>
<td>Bind with HashTable:</td>
<td>Bind with Dictionary:</td>
</tr>
<tr>
<td><asp:DropDownList runat="server" ID="ddlHashTable"></asp:DropDownList></td>
<td><asp:DropDownList runat="server" ID="ddlDictionary"></asp:DropDownList></td>
</tr>
</table>
</div>

Page looks like shown below

.Step2: Add following code in Button Click Event .cs page

 protected void Button1_Click(object sender, EventArgs e)

    {

        Hashtable hashtable = new Hashtable();

        hashtable.Add(1, "one");

        hashtable.Add(2, "two");

        hashtable.Add(3, "three");

        hashtable.Add(4, "four");

        hashtable.Add(5, "five");

        ddlHashTable.DataSource = hashtable;

        ddlHashTable.DataTextField = "key";

        ddlHashTable.DataValueField = "value";

        ddlHashTable.DataBind();

        Dictionary<int, string> dictionary = new Dictionary<int, string>();

        dictionary.Add(1, "one");

        dictionary.Add(2, "two");

        dictionary.Add(3, "three");

        dictionary.Add(4, "four");

        dictionary.Add(5, "five");

        ddlDictionary.DataSource = dictionary;

        ddlDictionary.DataTextField = "key";

        ddlDictionary.DataValueField = "value";

        ddlDictionary.DataBind();

       

    }

Step 3: Final Output get like these