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Editorial Team
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Asked: 2026-05-31T21:24:38+00:00

Hey guys I’m writing a simple web program to get my feet wet in

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Hey guys I’m writing a simple web program to get my feet wet in C#.Net and ASP.Net and I’m a little confused.

basically what I want to do is have a drop down box where the user can select the color they want the background of the page to be, but I can’t find the property to do it dynamically like that.

not that it matters but I’m using visual studio 2010.

Any ideas?

Please and thanks!

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

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void cmdSubmit_Click(object sender, EventArgs e)
    {
        if (txtName.Text == "")
        {

        }
        else
        {
            lblName.Visible = true;
            lblName.Text = "Well hello there " + txtName.Text + "!";
            lblColor.Visible = true;
            ddlColors.Visible = true;
        }
    }
    protected void ddlColors_SelectedIndexChanged(object sender, EventArgs e)
    {
        int strDdlValue = Convert.ToInt32(ddlColors.SelectedValue);
        switch (strDdlValue)
        {
            case 1:
                Body.Style["background-color"] = "Red";
                break;
            case 2:
                Body.Attributes["bgcolor"] = "blue";
                break;
            case 3:
                Body.Attributes["bgcolor"] = "magenta";
                break;
            case 4:
                Body.Attributes["bgcolor"] = "green";
                break;
            default:
                break;
        }
        lblBye.Visible = true;
    }
}

SOURCE:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.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></title>
</head>
<body id="Body" bgcolor="#3366ff" runat="server">
<form id="form1" runat="server" visible="True">
<div align="center" style="font-size: medium; font-weight: bold" >

    <asp:Label ID="lblWelcome" runat="server" Text="Welcome to WebGreeting!"></asp:Label>
    <br />
    <br />
    <br />
    <asp:Label ID="lblInstruction1" runat="server" 
        Text="Please enter your name in the text box below:"></asp:Label>
    <br />
    <asp:TextBox ID="txtName" runat="server"></asp:TextBox>
&nbsp;&nbsp;&nbsp;
    <asp:Button ID="cmdSubmit" runat="server" onclick="cmdSubmit_Click" Text="Submit!" />
    <br />
    <br />
    <br />
    <asp:Label ID="lblName" runat="server"></asp:Label>
    <br />
    <br />
    <br />
    <asp:Label ID="lblColor" runat="server" Text="What's your favorite color?" 
        Visible="False"></asp:Label>
    <br />
    <br />
    <br />
    <asp:DropDownList ID="ddlColors" runat="server" 
        onselectedindexchanged="ddlColors_SelectedIndexChanged" Visible="False">
        <asp:ListItem></asp:ListItem>
        <asp:ListItem>Red</asp:ListItem>
        <asp:ListItem>Green</asp:ListItem>
        <asp:ListItem>Blue</asp:ListItem>
        <asp:ListItem>Yellow</asp:ListItem>
    </asp:DropDownList>
    <br />
    <br />
    <br />
    <asp:Label ID="lblBye" runat="server" Text="I hope you had a nice day!" 
        Visible="False"></asp:Label>
    <br />

</div>
</form>
</body>
</html>
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1 Answer

  1. Editorial Team
    <html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
    <title>Untitled Page</title> 
</head> 
<body id="Body" runat="server"> 
<form id="form1" runat="server"> 
<div> 
    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" 
        onselectedindexchanged="DropDownList1_SelectedIndexChanged"> 
        <asp:ListItem>1</asp:ListItem> 
        <asp:ListItem>2</asp:ListItem> 
        <asp:ListItem>3</asp:ListItem> 
        <asp:ListItem>4</asp:ListItem> 
    </asp:DropDownList> 
</div> 
</form> 
</body> 
</html>

    Code Behind: 

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

    { 
    int strDdlValue = Convert.ToInt32(DropDownList1.SelectedValue); 
    switch (strDdlValue) 
        { 
        case 1: 
            Body.Attributes["bgcolor"] = "Red"; 
            break; 
        case 2: 
            Body.Attributes["bgcolor"] = "blue"; 
            break; 
        case 3: 
            Body.Attributes["bgcolor"] = "magenta"; 
            break; 
        case 4: 
            Body.Attributes["bgcolor"] = "green"; 
            break; 
        default: 
                        break; 
        } 
    }
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