wpf-devexpress-dot-xpf-dot-core-dot-dxtabcontrol-37bc1e9c.md
Occurs before the selected tab item is changed.
Namespace : DevExpress.Xpf.Core
Assembly : DevExpress.Xpf.Core.v25.2.dll
NuGet Package : DevExpress.Wpf.Core
public event TabControlSelectionChangingEventHandler SelectionChanging
Public Event SelectionChanging As TabControlSelectionChangingEventHandler
The SelectionChanging event's data class is TabControlSelectionChangingEventArgs. The following properties provide information specific to this event:
| Property | Description |
|---|---|
| Cancel | Gets or sets a value indicating whether the event should be canceled. Inherited from CancelEventArgs. |
| NewSelectedIndex | Gets the index of the tab item that is about to be selected. |
| NewSelectedItem | Gets the tab item to be selected. |
| OldSelectedIndex | Gets the index of the currently selected tab item. |
| OldSelectedItem | Gets the currently selected tab item. |
Handle the SelectionChanging event to prevent selecting a tab item. To do this, set the event parameter’s TabControlSelectionChangingEventArgs.Cancel property to true.
To obtain which tab item is being selected, use the event parameter’s TabControlSelectionChangingEventArgs.NewSelectedIndex property. The index of the previously selected tab item is returned by the event parameter’s TabControlSelectionChangedEventArgs.OldSelectedIndex property. Use the DXTabControl.GetTabItem method to obtain a tab item by its index.
After a tab item has been selected, the DXTabControl.SelectionChanged event is fired.
The following example handles the DXTabControl.SelectionChanging event and does not allow users to select tab items if their IsUrgent property is set to false.
<Window xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="DXTabControl_RestrictingSelection.MainWindow"
Title="MainWindow" Height="350" Width="525">
<Grid x:Name="LayoutRoot" Loaded="LayoutRoot_Loaded">
<dx:DXTabControl x:Name="tabControl" Height="140" Width="300"
SelectionChanging="tabControl_SelectionChanging">
<dx:DXTabControl.ItemHeaderTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=ProductName}" />
</DataTemplate>
</dx:DXTabControl.ItemHeaderTemplate>
<dx:DXTabControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="ID = " />
<TextBlock Text="{Binding Path=ID}" Foreground="Blue" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Price = " />
<TextBlock Text="{Binding Path=Price}" Foreground="Blue" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Discount = " />
<TextBlock Text="{Binding Path=Discount}" Foreground="Blue" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Order Date = " />
<TextBlock Text="{Binding Path=OrderDate}" Foreground="Blue" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Status = " />
<TextBlock Text="{Binding Path=Status}" Foreground="Blue" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Urgent = " />
<TextBlock Text="{Binding Path=IsUrgent}" Foreground="Blue" />
</StackPanel>
</StackPanel>
</DataTemplate>
</dx:DXTabControl.ItemTemplate>
<dx:DXTabControl.View>
<dx:TabControlScrollView ShowHeaderMenu="True" />
</dx:DXTabControl.View>
</dx:DXTabControl>
</Grid>
</Window>
using System.Windows;
using DevExpress.Xpf.Core;
using DXExample.DemoData;
namespace DXTabControl_RestrictingSelection {
public partial class MainWindow : Window {
public MainWindow() {
InitializeComponent();
}
private void LayoutRoot_Loaded(object sender, RoutedEventArgs e) {
tabControl.ItemsSource = Invoice.GetData();
}
private void tabControl_SelectionChanging(object sender,
TabControlSelectionChangingEventArgs e) {
if (!((Invoice)tabControl.Items[e.NewSelectedIndex]).IsUrgent)
e.Cancel = true;
}
}
}
Imports System.Windows
Imports DevExpress.Xpf.Core
Imports DXExample.DemoData
Namespace DXTabControl_RestrictingSelection
Partial Public Class MainWindow
Inherits Window
Public Sub New()
InitializeComponent()
End Sub
Private Sub LayoutRoot_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
tabControl.ItemsSource = Invoice.GetData()
End Sub
Private Sub tabControl_SelectionChanging(ByVal sender As Object, ByVal e As TabControlSelectionChangingEventArgs)
If Not CType(tabControl.Items(e.NewSelectedIndex), Invoice).IsUrgent Then
e.Cancel = True
End If
End Sub
End Class
End Namespace
using System;
using System.Collections.Generic;
namespace DXExample.DemoData {
public enum InvoiceStatus { Ordered, Payed, Shipped, Delivered, Invalidated }
public class Invoice {
public int ID { get; set; }
public string ProductName { get; set; }
public double Price { get; set; }
public DateTime OrderDate { get; set; }
public double Discount { get; set; }
public bool IsUrgent { get; set; }
public InvoiceStatus Status { get; set; }
static public List<Invoice> GetData() {
List<Invoice> data = new List<Invoice>();
data.Add(new Invoice() { ID = 0, ProductName = "Tofu", IsUrgent = false,
Price = 235.54, Discount = 9.4, Status = InvoiceStatus.Invalidated,
OrderDate = new DateTime(2009, 3, 12) });
data.Add(new Invoice() { ID = 1, ProductName = "Ravioli Angelo", IsUrgent = true,
Price = 178.45, Discount = 6.1, Status = InvoiceStatus.Delivered,
OrderDate = new DateTime(2009, 2, 9) });
data.Add(new Invoice() { ID = 2, ProductName = "Geitost", IsUrgent = false,
Price = 89.98, Discount = 5.4, Status = InvoiceStatus.Payed,
OrderDate = new DateTime(2009, 4, 1) });
data.Add(new Invoice() { ID = 3, ProductName = "Chang", IsUrgent = true,
Price = 189.33, Discount = 18.2, Status = InvoiceStatus.Shipped,
OrderDate = new DateTime(2009, 5, 23) });
data.Add(new Invoice() { ID = 4, ProductName = "Inlagd Sill", IsUrgent = false,
Price = 509.10, Discount = 22.2, Status = InvoiceStatus.Ordered,
OrderDate = new DateTime(2009, 6, 30) });
data.Add(new Invoice() { ID = 5, ProductName = "Alice Mutton", IsUrgent = true,
Price = 791.18, Discount = 24.4, Status = InvoiceStatus.Invalidated,
OrderDate = new DateTime(2009, 5, 7) });
return data;
}
}
}
Imports System
Imports System.Collections.Generic
Namespace DXExample.DemoData
Public Enum InvoiceStatus
Ordered
Payed
Shipped
Delivered
Invalidated
End Enum
Public Class Invoice
Public Property ID() As Integer
Public Property ProductName() As String
Public Property Price() As Double
Public Property OrderDate() As Date
Public Property Discount() As Double
Public Property IsUrgent() As Boolean
Public Property Status() As InvoiceStatus
Public Shared Function GetData() As List(Of Invoice)
Dim data As New List(Of Invoice)()
data.Add(New Invoice() With {.ID = 0, .ProductName = "Tofu", .IsUrgent = False, .Price = 235.54, .Discount = 9.4, .Status = InvoiceStatus.Invalidated, .OrderDate = New Date(2009, 3, 12)})
data.Add(New Invoice() With {.ID = 1, .ProductName = "Ravioli Angelo", .IsUrgent = True, .Price = 178.45, .Discount = 6.1, .Status = InvoiceStatus.Delivered, .OrderDate = New Date(2009, 2, 9)})
data.Add(New Invoice() With {.ID = 2, .ProductName = "Geitost", .IsUrgent = False, .Price = 89.98, .Discount = 5.4, .Status = InvoiceStatus.Payed, .OrderDate = New Date(2009, 4, 1)})
data.Add(New Invoice() With {.ID = 3, .ProductName = "Chang", .IsUrgent = True, .Price = 189.33, .Discount = 18.2, .Status = InvoiceStatus.Shipped, .OrderDate = New Date(2009, 5, 23)})
data.Add(New Invoice() With {.ID = 4, .ProductName = "Inlagd Sill", .IsUrgent = False, .Price = 509.10, .Discount = 22.2, .Status = InvoiceStatus.Ordered, .OrderDate = New Date(2009, 6, 30)})
data.Add(New Invoice() With {.ID = 5, .ProductName = "Alice Mutton", .IsUrgent = True, .Price = 791.18, .Discount = 24.4, .Status = InvoiceStatus.Invalidated, .OrderDate = New Date(2009, 5, 7)})
Return data
End Function
End Class
End Namespace
See Also