Using Reuseable Elements with User Controls in VB

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Using Reuseable Elements with User Controls in VB

ASP.NET Controls Tutorial

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. VB 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="VB" AutoEventWireup="true" CodeFile="ListPicker.ascx.vb" Inherits="ListPicker" %>
<table>

<tr>

Available<br /> <asp:ListBox ID="SourceList" runat="server" Height="200px" Width="200px"></asp:ListBox></td>

<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>

Selected<br />
<asp:ListBox ID="TargetList" runat="server" Height="200px" Width="200px"></asp:ListBox></td>

</tr>

</table>

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Now we add code to the controls:

Inherits System.Web.UI.UserControl
Protected Sub AddAll_Click(ByVal sender As Object, ByVal e As EventArgs)

TargetList.SelectedIndex = -1
For Each li As ListItem In SourceList.Items

AddItem(li)

Next li

End Sub
Protected Sub AddOne_Click(ByVal sender As Object, ByVal e As EventArgs)

If SourceList.SelectedIndex >= 0 Then

AddItem(SourceList.SelectedItem)

End If

End Sub
Protected Sub Remove_Click(ByVal sender As Object, ByVal e As EventArgs)

If TargetList.SelectedIndex >= 0 Then
TargetList.Items.RemoveAt(TargetList.SelectedIndex)
TargetList.SelectedIndex = -1
End If

End Sub
Protected Sub AddItem(ByVal li As ListItem)

TargetList.SelectedIndex = -1
If Me.AllowDuplicates = True Then

TargetList.Items.Add(li)

Else

If TargetList.Items.FindByText(li.Text) Is Nothing Then

TargetList.Items.Add(li)

End If

End Sub
Public ReadOnly Property SelectedItems() As ListItemCollection

Get

Return TargetList.Items

End Get

End Property
Public Property AllowDuplicates() As Boolean

Get

Return CType(ViewState("allowDuplicates"), Boolean)

End Get
Set(ByVal value As Boolean)

ViewState("allowDuplicates") = value

End Set

End Property
Public Sub AddSourceItem(ByVal sourceItem As String)

SourceList.Items.Add(sourceItem)

End Sub
Public Sub ClearAll()

SourceList.Items.Clear() TargetList.Items.Clear()

End Sub
Protected Sub RemoveSource_Click(ByVal sender As Object, ByVal e As EventArgs)

If SourceList.SelectedIndex >= 0 Then

SourceList.Items.RemoveAt(SourceList.SelectedIndex)
SourceList.SelectedIndex = -1

End If

End Sub

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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:

<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>

</div>
</form>

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ASPX code for these buttons should look something like this:

Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

End Sub
Protected Sub AllowDuplicates_CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)

ListPicker1.AllowDuplicates = AllowDuplicates.Checked

End Sub
Protected Sub AddItem_Click(ByVal sender As Object, ByVal e As EventArgs)

ListPicker1.AddSourceItem(Server.HtmlEncode(NewItem.Text))

End Sub
Protected Sub LoadFiles_Click(ByVal sender As Object, ByVal e As EventArgs)

Dim path As String = Server.MapPath(Request.ApplicationPath)
Dim files() As String = System.IO.Directory.GetFiles(path)
For Each filename As String In files

ListPicker1.AddSourceItem(filename)

Next filename

End Sub
Protected Sub ShowSelection_Click(ByVal sender As Object, ByVal e As EventArgs)

Dim selectedItemsString As String = ""
For Each lItem As ListItem In ListPicker1.SelectedItems

selectedItemsString &= "<br>" & lItem.Text

Next lItem
Selection.Text = selectedItemsString

End Sub
Protected Sub ClearSelection_Click(ByVal sender As Object, ByVal e As EventArgs)

ListPicker1.ClearAll()
Selection.Text = ""

End Sub

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