Fix for issue 2816 - Fixed template selector bug in TabItem styles (#2818)

* Fixed template selector bug in TabItem style

* Fixing same issue for RailTabItem

Author: nicolaihenriksen

MainDemo.Wpf/Domain/TabsViewModel.cs

@@ -0,0 +1,24 @@
+using System.Collections.ObjectModel;
+
+namespace MaterialDesignDemo.Domain;
+
+internal class TabsViewModel : ViewModelBase
+{
+    public ObservableCollection<CustomTab> CustomTabs { get; }
+
+    public CustomTab? SelectedTab { get; set; }
+
+    public TabsViewModel() =>
+        CustomTabs = new()
+        {
+            new CustomTab {CustomHeader = "Custom tab 1", CustomContent = "Custom tab 1 content"},
+            new CustomTab {CustomHeader = "Custom tab 2", CustomContent = "Custom tab 2 content"}
+        };
+}
+
+internal class CustomTab
+{
+    public string? CustomHeader { get; set; }
+
+    public string? CustomContent { get; set; }
+}

MainDemo.Wpf/Tabs.xaml

@@ -6,8 +6,10 @@
     xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:smtx="clr-namespace:ShowMeTheXAML;assembly=ShowMeTheXAML"
+    xmlns:domain="clr-namespace:MaterialDesignDemo.Domain"
     d:DesignHeight="4000"
     d:DesignWidth="1920"
+    d:DataContext="{d:DesignInstance Type=domain:TabsViewModel, IsDesignTimeCreatable=True}"
     mc:Ignorable="d">
     <StackPanel Margin="0,0,8,8">
 
@@ -505,5 +507,27 @@
                 </materialDesign:Card>
             </smtx:XamlDisplay>
         </StackPanel>
+
+        <TextBlock
+            Margin="0,15,0,20"
+            Style="{StaticResource MaterialDesignHeadline5TextBlock}"
+            Text="Custom items (and DisplayMemberPath)" />
+
+        <smtx:XamlDisplay Margin="0,0,0,16" UniqueKey="tabs_with_displaymemberpath">
+            <materialDesign:Card>
+                <TabControl
+                    ItemsSource="{Binding CustomTabs}"
+                    SelectedItem="{Binding SelectedTab}"
+                    HorizontalContentAlignment="Left"
+                    DisplayMemberPath="CustomHeader">
+                    <TabControl.ContentTemplate>
+                        <DataTemplate DataType="domain:CustomTab">
+                            <TextBlock Text="{Binding CustomContent}" FontSize="18" Margin="10" />
+                        </DataTemplate>
+                    </TabControl.ContentTemplate>
+                </TabControl>
+            </materialDesign:Card>
+        </smtx:XamlDisplay>
+
     </StackPanel>
 </UserControl>

MainDemo.Wpf/Tabs.xaml.cs

@@ -1,28 +1,15 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using System.Windows;
-using System.Windows.Controls;
-using System.Windows.Data;
-using System.Windows.Documents;
-using System.Windows.Input;
-using System.Windows.Media;
-using System.Windows.Media.Imaging;
-using System.Windows.Navigation;
-using System.Windows.Shapes;
+using MaterialDesignDemo.Domain;
 
-namespace MaterialDesignDemo
+namespace MaterialDesignDemo;
+
+/// <summary>
+/// Interaction logic for Tabs.xaml
+/// </summary>
+public partial class Tabs
 {
-    /// <summary>
-    /// Interaction logic for Tabs.xaml
-    /// </summary>
-    public partial class Tabs : UserControl
+    public Tabs()
     {
-        public Tabs()
-        {
-            InitializeComponent();
-        }
+        DataContext = new TabsViewModel();
+        InitializeComponent();
     }
-}
+}

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TabControl.xaml

@@ -266,7 +266,7 @@
                                 Content="{TemplateBinding Header}"
                                 ContentStringFormat="{TemplateBinding HeaderStringFormat}"
                                 ContentTemplate="{TemplateBinding HeaderTemplate}"
-                                ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
+                                ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}"
                                 Focusable="False"
                                 Opacity=".82"
                                 RecognizesAccessKey="True"
@@ -464,7 +464,7 @@
                                     Content="{TemplateBinding Header}"
                                     ContentStringFormat="{TemplateBinding HeaderStringFormat}"
                                     ContentTemplate="{TemplateBinding HeaderTemplate}"
-                                    ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
+                                    ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}"
                                     Focusable="False"
                                     Opacity=".52"
                                     RecognizesAccessKey="True"