Ensure there is at least one item selected : ListBox « Windows Presentation Foundation « VB.Net Tutorial

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VB.Net Tutorial » Windows Presentation Foundation » ListBox 
16.27.11.Ensure there is at least one item selected
<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF" Height="300" Width="300">
    <StackPanel>
        <ListBox FontSize="16" Height="150" Margin="5" Name="listBox1" SelectionMode="Extended">
            <ListBoxItem>List Item 1</ListBoxItem>
            <ListBoxItem>List Item 2</ListBoxItem>
            <ListBoxItem>List Item 3</ListBoxItem>
        </ListBox>
        <StackPanel HorizontalAlignment="Center" Orientation="Horizontal">
            <Label Content="_New item text:" VerticalAlignment="Center" Target="{Binding ElementName=textBox}"  />
            <TextBox Margin="5" Name="textBox" MinWidth="120" />            
        </StackPanel>
        <StackPanel HorizontalAlignment="Center" Orientation="Horizontal">
            <Button Click="btnAddListItem_Click" Content="Add Item" IsDefault="True" Margin="5" Name="btnAddListItem" />
            <Button Click="btnDeleteListItem_Click" Content="Delete Items" Margin="5" Name="btnDeleteListItem" />
            <Button Click="btnSelectAll_Click" Content="Select All" Margin="5" Name="btnSelectAll" />
        </StackPanel>
    </StackPanel>
</Window>
//File:Window.xaml.vb
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media

Namespace WpfApplication1
  Public Partial Class Window1
    Inherits Window
    Public Sub New()
      InitializeComponent()
    End Sub
    Private Sub btnAddListItem_Click(sender As Object, e As RoutedEventArgs)
      If textBox.Text.Length = Then
        MessageBox.Show("Enter text to add to the list.", Title)
      Else
        Dim item As New ListBoxItem()
        item.Content = textBox.Text
        item.IsSelected = True
        item.HorizontalAlignment = HorizontalAlignment.Center
        item.FontWeight = FontWeights.Bold
        item.FontFamily = New FontFamily("Tahoma")

        listBox1.Items.Add(item)

        textBox.Clear()
        textBox.Focus()
      End If
    End Sub

    Private Sub btnDeleteListItem_Click(sender As Object, e As RoutedEventArgs)
      If listBox1.SelectedItems.Count = Then
        MessageBox.Show("Select list items to delete.", Title)
      Else
        While listBox1.SelectedItems.Count > 0
          listBox1.Items.Remove(listBox1.SelectedItems(0))
        End While
      End If
    End Sub
    Private Sub btnSelectAll_Click(sender As Object, e As RoutedEventArgs)
      listBox1.SelectAll()
    End Sub
  End Class
End Namespace
WPF Ensure There Is At Least One Item Selected
16.27.ListBox
16.27.1.Bind String Array Resource to ListBoxBind String Array Resource to ListBox
16.27.2.Use Data Templates to Display Bound DataUse Data Templates to Display Bound Data
16.27.3.CheckBox ListCheckBox List
16.27.4.Convert the contents of a ListBoxItem to an instance of GridLength by using GridLengthConverterConvert the contents of a ListBoxItem to an instance of GridLength by using GridLengthConverter
16.27.5.Use the FontSizeConverter class to convert the content of a ListBoxItem to a value that represents the size of a font.Use the FontSizeConverter class to convert the content of a ListBoxItem to a value that represents the size of a font.
16.27.6.Convert contents of a ListBoxItem to an instance of Thickness by using the ThicknessConverterConvert contents of a ListBoxItem to an instance of Thickness by using the ThicknessConverter
16.27.7.DataTrigger, ListBox and user objectDataTrigger, ListBox and user object
16.27.8.Add selected file to ListBoxAdd selected file to ListBox
16.27.9.This list box allows items to be selected in groups by using the SHIFT key and mouse or the CTRL key and space key.This list box allows items to be selected in groups by using the SHIFT key and mouse or the CTRL key and space key.
16.27.10.Iterate through the selected items and remove each oneIterate through the selected items and remove each one
16.27.11.Ensure there is at least one item selectedEnsure there is at least one item selected
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