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Using Reuseable Elements with User Controls in C#
This tutorial will allow you to move data from one list box to another, as well as remove them again - either one by one, or altogether. Also, you can choose to allow duplicates or not, as well as output the chosen selection. C# version.
We need a Web User Control, which will have two list boxes, and four buttons: Add All, Add One, Delete One (from Selection List), and also Delete One (from Source List).
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="ListPicker.ascx.cs" Inherits="ListPicker" %>
<table>
<tr>
<td style="width: 100px">
Available<br /> <asp:ListBox ID="SourceList" runat="server" Height="200px" Width="200px"></asp:ListBox></td> <td style="width: 100px">
<asp:Button ID="AddAll" runat="server" OnClick="AddAll_Click" Text=">>" /> <asp:Button ID="AddOne" runat="server" OnClick="AddOne_Click" Text=" > " /> <asp:Button ID="Remove" runat="server" OnClick="Remove_Click" Text=" X " /><br /> <br /> <br /> <asp:Button ID="RemoveSource" runat="server" OnClick="RemoveSource_Click" Text="< X" /></td> <td style="width: 100px">
Selected<br /> <asp:ListBox ID="TargetList" runat="server" Height="200px" Width="200px"></asp:ListBox></td> </tr> |
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Now we add code to the controls:
protected void AddAll_Click(object sender, EventArgs e)
{
TargetList.SelectedIndex = -1; foreach(ListItem li in SourceList.Items) {
AddItem(li); }
protected void AddOne_Click(object sender, EventArgs e)
{
if(SourceList.SelectedIndex >= 0) {
AddItem(SourceList.SelectedItem); }
protected void Remove_Click(object sender, EventArgs e)
{
if(TargetList.SelectedIndex >= 0) {
TargetList.Items.RemoveAt(TargetList.SelectedIndex);
TargetList.SelectedIndex = -1; }
protected void AddItem(ListItem li)
{
TargetList.SelectedIndex = -1; if(this.AllowDuplicates == true) {
TargetList.Items.Add(li); } else {
if(TargetList.Items.FindByText(li.Text) == null) {
TargetList.Items.Add(li); } }
public ListItemCollection SelectedItems
{
get { return TargetList.Items; } }
public Boolean AllowDuplicates
{
get {
return (Boolean)ViewState["allowDuplicates"]; } set {
ViewState["allowDuplicates"] = value; }
public void AddSourceItem(String sourceItem)
{
SourceList.Items.Add(sourceItem); }
public void ClearAll()
{
SourceList.Items.Clear();
TargetList.Items.Clear(); }
protected void RemoveSource_Click(object sender, EventArgs e)
{
if (SourceList.SelectedIndex >= 0) {
SourceList.Items.RemoveAt(SourceList.SelectedIndex);
SourceList.SelectedIndex = -1; } |
Add the ListPicker Control onto an ASPX page and add a text box and button to allow user to add to the source list, a button to allow population of source list with list of files in the directory, a button to clear both list boxes, an Allow Duplicates check box, and a button & label to output the current selection:
<form id="form1" runat="server">
<div>
<uc1:ListPicker id="ListPicker1" Runat="server" AllowDuplicates="true" /> <asp:TextBox ID="NewItem" runat="server"> <asp:Button ID="AddItem" runat="server" OnClick="AddItem_Click" Text="Add Item" /><br /> <asp:Button ID="LoadFiles" runat="server" OnClick="LoadFiles_Click" Text="File List" /> <asp:Button
ID="ClearSelection" runat="server" OnClick="ClearSelection_Click" Text="Clear All" /><br /> <asp:CheckBox ID="AllowDuplicates" runat="server" AutoPostBack="True" Checked="True"
OnCheckedChanged="AllowDuplicates_CheckedChanged" Text="Allow Duplicates" /><br /> <asp:Button ID="ShowSelection" runat="server" OnClick="ShowSelection_Click" Text="Show Selection" /> <asp:Label ID="Selection" runat="server"></asp:Label>
</form> |
ASPX code for these buttons should look something like this:
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protected void AllowDuplicates_CheckedChanged(object sender, EventArgs e)
{
ListPicker1.AllowDuplicates = AllowDuplicates.Checked; }
protected void AddItem_Click(object sender, EventArgs e)
{
ListPicker1.AddSourceItem(Server.HtmlEncode(NewItem.Text)); }
protected void LoadFiles_Click(object sender, EventArgs e)
{
String path = Server.MapPath(Request.ApplicationPath); String[] files = System.IO.Directory.GetFiles(path); foreach(String filename in files) {
ListPicker1.AddSourceItem(filename); }
protected void ShowSelection_Click(object sender, EventArgs e)
{
String selectedItemsString = ""; foreach(ListItem lItem in ListPicker1.SelectedItems) {
selectedItemsString += "<br>" + lItem.Text; } Selection.Text = selectedItemsString;
protected void ClearSelection_Click(object sender, EventArgs e)
{
ListPicker1.ClearAll();
Selection.Text = ""; } |
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