ASP.NET Tutorial/ASP.net Controls/ListItem

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Add asp:ListItem to asp:DropDownList

<%@ Page Language="VB" Trace="true" %>
<!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 id="Head1" runat="server">
    <title>Show Control Tree</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:DropDownList
        id="DropDownList1"
        Runat="server">
        <asp:ListItem Text="Oranges" />
        <asp:ListItem Text="Apples" />
    </asp:DropDownList>    
    <asp:Button 
        id="Button1"
        Text="Submit"
        Runat="server" />
   
    </div>
    </form>
</body>
</html>


All items and selected item in a selectable control

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="SelectableListControls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
  <div>
    <asp:ListBox runat="server" 
                 ID="Listbox1" 
                 SelectionMode="Multiple" 
                 Rows="5">
        <asp:ListItem Selected="true">Option 1</asp:ListItem>
        <asp:ListItem>Option 2</asp:ListItem>
    </asp:ListBox>
    <br/><br/>
    <asp:DropDownList runat="server" ID="DropdownList1">
        <asp:ListItem Selected="true">Option 1</asp:ListItem>
        <asp:ListItem>Option 2</asp:ListItem>
    </asp:DropDownList>
    <br/><br/>
    <asp:CheckBoxList runat="server" 
                      ID="CheckboxList1" 
                      RepeatColumns="3" >
        <asp:ListItem Selected="true">Option 1</asp:ListItem>
       <asp:ListItem>Option 2</asp:ListItem>
    </asp:CheckBoxList>
    <br/>
    <asp:RadioButtonList runat="server" 
                         ID="RadiobuttonList1"
                         RepeatDirection="Horizontal" 
                         RepeatColumns="2">
        <asp:ListItem Selected="true">Option 1</asp:ListItem>
        <asp:ListItem>Option 2</asp:ListItem>
    </asp:RadioButtonList>
    <asp:Button ID="Button1" runat="server" Text="Submit" OnClick="Button1_Click"/>
  </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class SelectableListControls : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    if (!Page.IsPostBack)
    {
      for (int i = 3; i <= 5; i++)
      {
        Listbox1.Items.Add("Option " + i.ToString());
        DropdownList1.Items.Add("Option " + i.ToString());
        CheckboxList1.Items.Add("Option " + i.ToString());
        RadiobuttonList1.Items.Add("Option " + i.ToString());
      }
    }
    }
  protected void Button1_Click(object sender, System.EventArgs e)
  {
    Response.Write("<b>Selected items for Listbox1:</b><br/>");
    foreach (ListItem li in Listbox1.Items)
    {
      if (li.Selected) Response.Write("- " + li.Text + "<br/>");
    }
    Response.Write("<b>Selected item for DropdownList1:</b><br/>");
    Response.Write("- " + DropdownList1.SelectedItem.Text + "<br/>");
    Response.Write("<b>Selected items for CheckboxList1:</b><br/>");
    foreach (ListItem li in CheckboxList1.Items)
    {
      if (li.Selected) Response.Write("- " + li.Text + "<br/>");
    }
    Response.Write("<b>Selected item for RadiobuttonList1:</b><br/>");
    Response.Write("- " + RadiobuttonList1.SelectedItem.Text + "<br/>");
  }
}


A simple BulletedList control

<%@ Page Language="C#" %>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>BulletedList Server Control</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:BulletedList ID="Bulletedlist1" Runat="server">
            <asp:ListItem>United States</asp:ListItem>
            <asp:ListItem>United Kingdom</asp:ListItem>
            <asp:ListItem>Finland</asp:ListItem>
            <asp:ListItem>Russia</asp:ListItem>
            <asp:ListItem>Sweden</asp:ListItem>
            <asp:ListItem>Estonia</asp:ListItem>
        </asp:BulletedList>
    </form>
</body>
</html>


Change style for ListItem

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="ListControlAttributes" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label ID="myLab" runat="server" /><br />
        <asp:DropDownList ID="myDrop" runat="server">
            <asp:ListItem>Red</asp:ListItem>
            <asp:ListItem>Blue</asp:ListItem>
            <asp:ListItem>Green</asp:ListItem>            
        </asp:DropDownList>
        
    </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class ListControlAttributes : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    myLab.Text = "Red text here";
    myLab.Attributes["style"] = "background-color:red;";
    myDrop.Items[0].Attributes["style"] = "background-color:red;";
    myDrop.Items[1].Attributes["style"] = "background-color:green;";
    myDrop.Items[2].Attributes["style"] = "background-color:blue;";
    myDrop.Attributes["style"] = "background-color:yellow;";
    myDrop.Items[1].Enabled = false;
    }
}


Declaring List Items

The ListItem control supports the following five properties:
Attributes: attributes of a list item.
Enabled:    disable or enable a list item.
Selected:   mark as selected.
Text:       text displayed by the list item.
Value:      specify a hidden value associated with the list item.

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Favorite Product</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Label
        id="lblProducts"
        Text="Favorite Product:"
        AssociatedControlID="rblProducts"
        Runat="server" />
    <asp:RadioButtonList
        id="rblProducts"
        Runat="server">
        <asp:ListItem
            Text="The Remains of the Day"
            Value="product1" />
        <asp:ListItem
            Text="Star Wars"
            Value="product2" />
        <asp:ListItem
            Text="Pulp Fiction"
            Value="product3" />
    </asp:RadioButtonList>
    </div>
    </form>
</body>
</html>


Disabling certain ListItems from a collection (C#)

<%@ Page Language="C#" %>
<script runat="server">
    protected void Dropdownlist1_SelectedIndexChanged(object sender, EventArgs e)
    {
        Response.Write("You selected item number " + DropDownList1.SelectedValue + "<br>");
        Response.Write("You didn"t select item number " + DropDownList1.Items[1].Value);
    }
</script>
<html>
<head id="Head1" runat="server">
    <title>DropDownList Server Control</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:DropDownList ID="DropDownList1" Runat="server" AutoPostBack="True" OnSelectedIndexChanged="Dropdownlist1_SelectedIndexChanged">
            <asp:ListItem Value="1">First Choice</asp:ListItem>
            <asp:ListItem Value="2" Enabled="False">Second Choice</asp:ListItem>
            <asp:ListItem Value="3">Third Choice</asp:ListItem>
        </asp:DropDownList>
    </form>
</body>
</html>


Disabling certain ListItems from a collection (VB)

<%@ page language="VB" %>
<script runat="server">
    Protected Sub Dropdownlist1_SelectedIndexChanged(ByVal sender As Object, _
       ByVal e As System.EventArgs)
         Response.Write("You selected item number " & _
           DropDownList1.SelectedValue & "<br>")
         Response.Write("You didn"t select item number " & _
           DropDownList1.Items(1).Value)
    End Sub
</script>
<html>
<head id="Head1" runat="server">
    <title>DropDownList Server Control</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:DropDownList ID="Dropdownlist1" Runat="server" AutoPostBack="True" 
         OnSelectedIndexChanged="Dropdownlist1_SelectedIndexChanged">
            <asp:ListItem Value="1">First Choice</asp:ListItem>
            <asp:ListItem Value="2" Enabled="False">Second Choice</asp:ListItem>
            <asp:ListItem Value="3">Third Choice</asp:ListItem>
        </asp:DropDownList>
    </form>
</body>
</html>


Set style for label

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="ListControlProgrammatic" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Programmatic Iteration of ListControl</title>
</head>
<body>
    <form id="form1" runat="server">
    <div id="container">   
    <h1>Choose multiple colors (use ctrl or shift): </h1> 
    <asp:ListBox ID="myList" runat="server" 
       SelectionMode="Multiple" Rows="6">        
        <asp:ListItem Value="#FF0000">Red</asp:ListItem>
        <asp:ListItem Value="#FF00FF">Magenta</asp:ListItem>
        <asp:ListItem Value="#FFFF00">Yellow</asp:ListItem>
        <asp:ListItem Value="#00FF00">Green</asp:ListItem>
        <asp:ListItem Value="#00FFFF">Cyan</asp:ListItem>
        <asp:ListItem Value="#0000FF">Blue</asp:ListItem>
    </asp:ListBox>
    <asp:Button ID="myBtn" runat="server" Text="Submit"/>
    <asp:Label ID="labResult" runat="server" Width="300" Height="100" />
    </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class ListControlProgrammatic : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    if (IsPostBack)
    {
      labResult.Text = "Colors chosen: <br/>";
      foreach (ListItem li in myList.Items)
      {
        if (li.Selected)
        {
          labResult.Text += "<span style="color:";
          labResult.Text += li.Value + "">" + li.Text;
          labResult.Text += "</span><br/>";
        }
      }
    }
    }
}


Using the LinkButton value for the DisplayMode attribute (C#)

<%@ Page Language="C#" %>
<script runat="server">
    protected void BulletedList1_Click(object sender,
       System.Web.UI.WebControls.BulletedListEventArgs e)
    {    
         Label1.Text = "The index of item you selected: " + e.Index +
            "<br>The value of the item selected: " + 
            BulletedList1.Items[e.Index].Text;
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>BulletedList Server Control</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:BulletedList ID="BulletedList1" Runat="server" 
         OnClick="BulletedList1_Click" DisplayMode="LinkButton">
            <asp:ListItem>United States</asp:ListItem>
            <asp:ListItem>United Kingdom</asp:ListItem>
            <asp:ListItem>Finland</asp:ListItem>
        </asp:BulletedList>
        <asp:Label ID="Label1" Runat="server">
        </asp:Label>
    </form>
</body>
</html>


Using the LinkButton value for the DisplayMode attribute (VB)

<%@ Page Language="VB"%>
<script runat="server">
    Protected Sub BulletedList1_Click(ByVal sender As Object, _
       ByVal e As System.Web.UI.WebControls.BulletedListEventArgs)
        
        Label1.Text = "The index of item you selected: " & e.Index & _
           "<br>The value of the item selected: " & _
           BulletedList1.Items(e.Index).Text
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>BulletedList Server Control</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:BulletedList ID="BulletedList1" Runat="server" 
         OnClick="BulletedList1_Click" DisplayMode="LinkButton">
            <asp:ListItem>United States</asp:ListItem>
            <asp:ListItem>United Kingdom</asp:ListItem>
            <asp:ListItem>Finland</asp:ListItem>
        </asp:BulletedList>
        <asp:Label ID="Label1" Runat="server">
        </asp:Label>
    </form>
</body>
</html>
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ASP.net_Controls/ListItem&oldid=3377»