1. Aspx File :

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Drop_Down.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head runat="server">
 <title>Working with Dropdown Controls </title>
 <style type="text/css">
 table
 {
font-family: Arial;
font-size: 12px;
border: solid 1px #ccc;
}
td
 {
height: 30px;
text-align: center;
font-weight: bold;
border: solid 1px #ccc;
}
a
 {
color: Black;
text-decoration: none;
}
a:hover
 {
color: Red;
text-decoration: underline;
}
a:visited
 {
color: Purple;
text-decoration: underline;
}
</style>
 </head>
<body>
 <form id="form1" runat="server">
 <asp:ScriptManager ID="ScriptManager1" runat="server">
 </asp:ScriptManager>
 <table width="500px" cellpadding="5" cellspacing="5" align="center">
 <tr>
 <td colspan="2" style="background: #999; color: #ffffff;">
 <b>Change Face Color & Background Color through below Example </b>
 </td>
 </tr>
 <tr>
 <td>
 <asp:LinkButton ID="Drop_lnkbtn" runat="server" OnClick="Drop_lnkbtn_Click">Dropdown list Example </asp:LinkButton>
 </td>
 <td>
 <asp:LinkButton ID="Radio_lnkbtn" runat="server"
OnClick="Radio_lnkbtn_Click">Radio Button Example </asp:LinkButton>
 </td>
 </tr>
 </table>
 <asp:PlaceHolder ID="Place_Dropdown" runat="server">
 <table width="500px" cellpadding="5" cellspacing="5" align="center">
 <tr>
 <td colspan="4">
 Change Face Color & Background Color through Dropdown List
</td>
 </tr>
 <tr>
 <td>
 Face Color :
</td>
 <td>
 <asp:DropDownList ID="drop_down" runat="server" AutoPostBack="true" OnSelectedIndexChanged="drop_down_SelectedIndexChanged">
 <asp:ListItem> Red </asp:ListItem>
 <asp:ListItem> Green </asp:ListItem>
 <asp:ListItem> Blue </asp:ListItem>
 <asp:ListItem> Black </asp:ListItem>
 <asp:ListItem> Yellow </asp:ListItem>
 <asp:ListItem> Orange </asp:ListItem>
 </asp:DropDownList>
 </td>
 <td>
 Back Color :
</td>
 <td>
 <asp:DropDownList ID="drop_Background" runat="server" AutoPostBack="true" OnSelectedIndexChanged="drop_Background_SelectedIndexChanged">
 <asp:ListItem> Red </asp:ListItem>
 <asp:ListItem> Green </asp:ListItem>
 <asp:ListItem> Blue </asp:ListItem>
 <asp:ListItem> Black </asp:ListItem>
 <asp:ListItem> Yellow </asp:ListItem>
 <asp:ListItem> Orange </asp:ListItem>
 </asp:DropDownList>
 </td>
 </tr>
 <tr>
 <td colspan="4">
 <asp:Label ID="lbl" runat="server" BackColor="AliceBlue" Text="Label" Font-Size="16px"></asp:Label>
 </td>
 </tr>
 </table>
 </asp:PlaceHolder>
 <asp:PlaceHolder ID="Place_Radiobtn" runat="server">
 <table width="500px" cellpadding="5" cellspacing="5" align="center">
 <tr>
 <td colspan="4">
 Change Face Color & Background Color through Radio Button List
</td>
 </tr>
 <tr>
 <td>
 Face Color :
</td>
 <td>
 <asp:RadioButtonList ID="face_radio" runat="server" AutoPostBack="true" OnSelectedIndexChanged="face_radio_SelectedIndexChanged">
 <asp:ListItem> Red </asp:ListItem>
 <asp:ListItem> Green </asp:ListItem>
 <asp:ListItem> Blue </asp:ListItem>
 <asp:ListItem> Black </asp:ListItem>
 <asp:ListItem> Yellow </asp:ListItem>
 <asp:ListItem> Orange </asp:ListItem>
 </asp:RadioButtonList>
 </td>
 <td>
 Back Color :
</td>
 <td>
 <asp:RadioButtonList ID="back_radio" runat="server" AutoPostBack="true"
OnSelectedIndexChanged="back_radio_SelectedIndexChanged">
 <asp:ListItem> Red </asp:ListItem>
 <asp:ListItem> Green </asp:ListItem>
 <asp:ListItem> Blue </asp:ListItem>
 <asp:ListItem> Black </asp:ListItem>
 <asp:ListItem> Yellow </asp:ListItem>
 <asp:ListItem> Orange </asp:ListItem>
 </asp:RadioButtonList>
 </td>
 </tr>
 <tr>
 <td colspan="4">
 <asp:Label ID="lblradio" runat="server" BackColor="AliceBlue" Text="Label"
Font-Size="16px"></asp:Label>
 </td>
 </tr>
 </table>
 </asp:PlaceHolder>
 </form>
 </body>
</html>

2. CS File :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
lbl.Visible = false;
lblradio.Visible = false;
Place_Dropdown.Visible = false;
Place_Radiobtn.Visible = false;
}

}
protected void drop_down_SelectedIndexChanged(object sender, EventArgs e)
{
lbl.Visible = true;
string s = drop_down.SelectedItem.Text.ToString();
lbl.ForeColor = System.Drawing.Color.FromName(s) ;
lbl.Text ="This Color is :" + s;
drop_down.ForeColor = System.Drawing.Color.FromName(s);

}
protected void drop_Background_SelectedIndexChanged(object sender, EventArgs e)
{
string s1 = drop_Background.SelectedItem.Text.ToString();
lbl.BackColor = System.Drawing.Color.FromName(s1);
lbl.Text = "Background Color is :" + s1;
drop_Background.BackColor = System.Drawing.Color.FromName(s1);
}
protected void face_radio_SelectedIndexChanged(object sender, EventArgs e)
{
lblradio.Visible = true;
string face = face_radio.SelectedItem.Text.ToString();
lblradio.ForeColor = System.Drawing.Color.FromName(face);
lblradio.Text = "Selected Color is :" + face;
face_radio.ForeColor = System.Drawing.Color.FromName(face);
}
protected void back_radio_SelectedIndexChanged(object sender, EventArgs e)
{
string back = back_radio.SelectedItem.Text.ToString();
lblradio.BackColor = System.Drawing.Color.FromName(back);
lblradio.Text = "Background Color is :" + back;
back_radio.BackColor = System.Drawing.Color.FromName(back);
}
protected void Drop_lnkbtn_Click(object sender, EventArgs e)
{
Place_Dropdown.Visible = true;
Place_Radiobtn.Visible = false;
}
protected void Radio_lnkbtn_Click(object sender, EventArgs e)
{
Place_Dropdown.Visible = false;
Place_Radiobtn.Visible = true;
}
}