How to Stretch WPF Tab Item Headers to Parent Control Width

Question

Is there a way in XAML to cause the tab item headers to stretch across the width of the tab control?

For example, I have three tabs: red, blue and green. If I have a tab control with its width set to auto, the tab headers will only fill up part of the space above the tab content, but I want them to fill up all the space. For my three tab example, red should take up the first third of the control, blue should take up the center third, and green the final third.

I have an idea how to do this in a code behind which I am working on now, but I am interested in doing this the easiest way possible.

Stoichiometric

Answer 1

I took Jordan's example and made some changes to it. This version should work for any number of tabs:

namespace WpfApplication1.Converters
{
    public class TabSizeConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter,
            System.Globalization.CultureInfo culture)
        {
            TabControl tabControl = values[0] as TabControl;
            double width = tabControl.ActualWidth / tabControl.Items.Count;
            //Subtract 1, otherwise we could overflow to two rows.
            return (width <= 1) ? 0 : (width - 1);
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter,
            System.Globalization.CultureInfo culture)
        {
            throw new NotSupportedException();
        }
    }
}

Same namespace in the xaml:

xmlns:local="clr-namespace:WpfApplication1.Converters"

And this will make all tabs use it:

<Window.Resources>
    <local:TabSizeConverter x:Key="tabSizeConverter" />
    <Style TargetType="{x:Type TabItem}">
        <Setter Property="Width">
            <Setter.Value>
                <MultiBinding Converter="{StaticResource tabSizeConverter}">
                    <Binding RelativeSource="{RelativeSource Mode=FindAncestor,
            AncestorType={x:Type TabControl}}" />
                    <Binding RelativeSource="{RelativeSource Mode=FindAncestor,
            AncestorType={x:Type TabControl}}" Path="ActualWidth" />
                </MultiBinding>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

Paulinepauling

I would cap the return value of the converter with return width < 0 ? 0 : width - 1 otherwise it could raise an exception – Ferbam

Will the width ever actually be less than 0 though? It might be able to, but either way I'll include this but with a minor modification. It should actually be return (width <= 1) ? 0 : (width - 1); in case width is between 0 and 1 to prevent a negative result. – Paulinepauling

when using this the tabitems stack on top of each other, but if i change the (width - 1) to (width - 2.1) then it "works", but i appear to have one pixel space on either side of the tabitems. something i'm not doing correctly? – Groot

I get the same result as @Groot when the number of tab items is <= 3. With four and above it works great. I've changed my result to be: return (width <= 1) ? 0 : (width - 1.34); which seems to take care of all numbers of tab items. – Darell

@RyanVersaw:Simply Awesome :) – Impress

@RyanVersaw: Why not implementing IValueConverter instead of IMultiValueConverter? – Bayard

@Olivier If you would have asked me four years ago, I might have had a good answer for you! I haven't touched WPF in years, but if I had to guess, it may have had to do with the MultiBinding? Sorry, I really can't say a whole lot at this point. – Paulinepauling

replace return (width <= 1) ? 0 : (width - 1); to Math.Max(0, width) – Telling

I want to put this on my ResourceDictionary (TabControlStyles.xaml).. How? – Colettacolette

The reason it's an IMultiValueConverter and not an IValueConverter is that without the second binding to ActualWidth the binding will bind before the control is rendered, resulting in ActualWidth always being zero inside the converter. Adding the second binding to ActualWidth forces the binding to re-evaluate every time the width of the parent TabControl changes. It's a bit of a bodge but it works. – Remotion

Answer 2

Everyone seems to be going the converter route, but it really is as simple as using a UniformGrid with Rows set to 1 in the TabControl template, in place of the TabPanel. Of course, you will have to re-template it, but this isn't too bad.

Lawana

It works perfectly and it is so much simpler (given that you like to mess up with templates.. but you do, right ?) – Sheepfold

An example of this would be nice, for those that like to copy and paste :) – Suez

Example of usage: #28497309 – Suez

Wow, so much easier and more reliable than the converters approach, thanks! – Slav

Easier and doesn't even require interaction with C#. Just perfect solution. – Petronille

Answer 3

I am an old school style guy. and prefer this kind of functionality to encapsulate into the code of the control itself. My derived control looks like following:

    public class CustomTabControl :TabControl
{
    protected override void OnRenderSizeChanged(System.Windows.SizeChangedInfo sizeInfo)
    {
        foreach (TabItem item in this.Items)
        {
            double newW = (this.ActualWidth / Items.Count) - 1;
            if (newW < 0) newW = 0;

            item.Width = newW;
        }            
    }       
}

and my XAML looks like

</infrastructure:CustomTabControl>
     <TabItem />
     <TabItem />
</infrustracture:CustomControl>

Can someone explain why everyone prefers styling control instead of deriving.

Mangle

Answer 4

I was able to do this using a Converter like so:

namespace WpfApplication1.Converters
{
    public class SizeConverter : IValueConverter
    {
        #region IValueConverter Members

        public object Convert(object value, Type targetType, object parameter,
            System.Globalization.CultureInfo culture)
        {
            double width = Double.Parse(value.ToString());
            //Subtract 1, otherwise we could overflow to two rows.
            return .25 * width - 1;
        }

        public object ConvertBack(object value, Type targetType, object parameter,
            System.Globalization.CultureInfo culture)
        {
            throw new NotSupportedException();
        }

        #endregion
    }
}

Then adding the namespace to my xaml:

xmlns:local="clr-namespace:WpfApplication1.Converters"

Then making all of the TabItems use the converter:

<Window.Resources>
        <local:SizeConverter x:Key="sizeConverter" />
        <Style TargetType="{x:Type TabItem}">
            <Setter Property="Width" Value="{Binding ElementName=x_Grid, Path=ActualWidth, Converter={StaticResource sizeConverter}}" />
        </Style>
    </Window.Resources>

x_Grid is the x:Name of the parent element I want the tabs to be 1/4 of, if that makes sense.

Sage

I apologize for the tremendous amount of whitespace below the code. I don't know why it's doing that. – Sage

Also, you can make the converter as complicated as you want. You could go get the TabControl, look at its Items and see how many there are, and then use that to calculate your width. – Sage

Jordan: Thanks mate, this works a treat :) P.S. "Object Value" comes into the Convert function as a double, so you can just cast it "double height = (double)value;" +1 BTW :) – Wives

Answer 5

This is the most swift solution:

<TabControl.Template>
    <ControlTemplate TargetType="TabControl">
        <DockPanel>
            <UniformGrid IsItemsHost="True" Rows="1" DockPanel.Dock="Top"></UniformGrid>
            <ContentPresenter ContentSource="SelectedContent"></ContentPresenter>
        </DockPanel>
    </ControlTemplate>
</TabControl.Template>

Teleplay

I experience some unexpected behavior with this. Changing an ancestor TabControl whose tabs contain this templated TabControl, result in the templated TabControl changing tabs. Anyone knows why that happens? – Protuberate

Answer 6

It is possible by binding the width to the ActualWidth of the parent tab control as shown below.

I have wrapped it in a style to apply to all tab pages.

<Grid>
      <Grid.Resources>
        <Style TargetType="TabItem">
            <Setter Property="Width" Value="{Binding    
                     Path=ActualWidth,    
                     RelativeSource={RelativeSource    
                    Mode=FindAncestor,    
                    AncestorType={x:Type TabControl}}}"/>
        </Style>
    </Grid.Resources>

<TabControl>
    <TabItem Header="Page3"/>
    <TabItem Header="Page2"/>
    <TabItem Header="Page3"/>            
</TabControl> 
</Grid>

Edna

This would just make every TabItem occupy the full width. What is needed, they need to share the width. – Ferbam

Answer 7

I have solved this problem by creating a special converter:

    public class TabItemWidthAdjustmentConverter : IValueConverter
    {
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        Double lTabControlWidth = value is Double ? (Double)value : 50; // 50 just to see something, in case of error
        Int32 lTabsCount = (parameter != null && parameter is String) ? Int32.Parse((String)parameter) : 1;
        return lTabControlWidth / lTabsCount;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
    }

And I calculate the value of one tab item in the Tag element of the TabControl, to avoid calculating it for each tab separately. Here is the sample code (Note that In my case I needed a horizontal ScrollViewer, because I have multiple tab items, and with a minimum width):

<TabControl Name="tabControl" VerticalAlignment="Stretch" SelectionChanged="TabControl_SelectionChanged" 
                    Tag="{Binding RelativeSource={RelativeSource Self}, Path=ActualWidth, Converter={StaticResource tabItemWidthAdjustmentConverter}, ConverterParameter=15}"><!-- Here 15 because I have 15 tabs -->
            <TabControl.Template>
                <ControlTemplate TargetType="TabControl">
                    <StackPanel>
                        <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Disabled">
                            <TabPanel x:Name="HeaderPanel"
                                      Panel.ZIndex="1"
                                      KeyboardNavigation.TabIndex="1"
                                      IsItemsHost="True"/>
                        </ScrollViewer>
                        <ContentPresenter x:Name="PART_SelectedContentHost" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
                                          Margin="{TemplateBinding Padding}"
                                          ContentSource="SelectedContent"/>
                    </StackPanel>
                </ControlTemplate>
            </TabControl.Template>
            <TabItem Header="Tab1" MinWidth="115" VerticalAlignment="Stretch" Width="{Binding ElementName=tabControl, Path=Tag}">
                <ContentControl ContentTemplate="{StaticResource My_TemplateTab1}">
                    <ContentPresenter />
                </ContentControl>
            </TabItem>
            <TabItem Header="Tab2" MinWidth="115" Height="50" Width="{Binding ElementName=tabControl, Path=Tag}">
                <ContentControl ContentTemplate="{StaticResource My_TemplateTab2}">
                    <ContentPresenter />
                </ContentControl>
            </TabItem>
            <!-- Here another 13 tabs which I skipped -->
            </TabControl>

I can say that this works like a charm in my case :) Hope someone will find it useful!

P.S. I did not need/want any style in my case.

Merilee

Your solution is the only one which kind of worked! Thanks a lot. The only problem I encountered is that the ActualWidth of the TabControl is zero on initialization. When I retrieved the ActualWidth in the Loaded event handler, it is 450. Do you know why / how to solve that? – Whited

Please read the description of the WPF window events in here (espetially Initialized and Loaded): blogs.msdn.com/b/mikehillberg/archive/2006/09/19/… – Merilee

Your point is that, that what is happening is logical? At least that is what I make up out of the blog post (Thanks for that by the way) Since it is some days ago already I don't know why it was a problem for me. It is working good now, with the code in the Loaded event. Thanks! :-) – Whited

Yep this is logical. It means that you somehow in your code accessed ActualWidth before you had any actual value in it. Happy it works for you now! – Merilee

Answer 8

Here is a painless solution that uses Templates only:

<Window x:Class="Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:EffectLibrary="clr-namespace:EffectLibrary;assembly=EffectLibrary"
        mc:Ignorable="d"
        Title="Window1" Height="300" Width="300">
    <TabControl Style="{DynamicResource TabControlStyle}" ItemContainerStyle="{DynamicResource TabItemStyle}" BorderBrush="{DynamicResource Pallete.Primary}" Foreground="{DynamicResource Pallete.Primary}" Background="Transparent" Margin="0" d:LayoutOverrides="Height">
        <TabControl.Resources>
            <Style x:Key="TabControlStyle" TargetType="{x:Type TabControl}">
                <Setter Property="Padding" Value="0"/>
                <Setter Property="HorizontalContentAlignment" Value="Center"/>
                <Setter Property="VerticalContentAlignment" Value="Center"/>
                <Setter Property="Background" Value="Transparent"/>
                <Setter Property="BorderBrush" Value="#093A5F"/>
                <Setter Property="BorderThickness" Value="1"/>
                <Setter Property="Foreground" Value="#001423"/>
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type TabControl}">
                            <Border x:Name="Bg" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}">
                                <Grid x:Name="templateRoot" ClipToBounds="true" SnapsToDevicePixels="true" KeyboardNavigation.TabNavigation="Local">
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition x:Name="ColumnDefinition0"/>
                                        <ColumnDefinition x:Name="ColumnDefinition1" Width="0"/>
                                    </Grid.ColumnDefinitions>
                                    <Grid.RowDefinitions>
                                        <RowDefinition x:Name="RowDefinition0" Height="Auto"/>
                                        <RowDefinition x:Name="RowDefinition1" Height="*"/>
                                    </Grid.RowDefinitions>
                                    <UniformGrid x:Name="headerPanel" IsItemsHost="True" Margin="0">
                                        <UniformGrid.Style>
                                            <Style TargetType="{x:Type UniformGrid}">
                                                <Setter Property="Rows" Value="1"/>
                                                <Style.Triggers>
                                                    <DataTrigger Binding="{Binding TabStripPlacement, RelativeSource={RelativeSource TemplatedParent}}" Value="Right">
                                                        <Setter Property="Columns" Value="1"/>
                                                        <Setter Property="Rows" Value="0"/>
                                                    </DataTrigger>
                                                    <DataTrigger Binding="{Binding TabStripPlacement, RelativeSource={RelativeSource TemplatedParent}}" Value="Left">
                                                        <Setter Property="Columns" Value="1"/>
                                                        <Setter Property="Rows" Value="0"/>
                                                    </DataTrigger>
                                                </Style.Triggers>
                                            </Style>
                                        </UniformGrid.Style>
                                    </UniformGrid>
                                    <Border x:Name="contentPanel" Grid.Column="0" KeyboardNavigation.DirectionalNavigation="Contained" Grid.Row="1" KeyboardNavigation.TabIndex="2" KeyboardNavigation.TabNavigation="Local" BorderThickness="0,1,0,0" BorderBrush="{TemplateBinding BorderBrush}">
                                        <ContentPresenter x:Name="PART_SelectedContentHost" ContentSource="SelectedContent" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                                    </Border>
                                </Grid>
                            </Border>
                            <ControlTemplate.Triggers>
                                <Trigger Property="TabStripPlacement" Value="Bottom">
                                    <Setter Property="Grid.Row" TargetName="headerPanel" Value="1"/>
                                    <Setter Property="Grid.Row" TargetName="contentPanel" Value="0"/>
                                    <Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
                                    <Setter Property="Height" TargetName="RowDefinition1" Value="Auto"/>
                                </Trigger>
                                <Trigger Property="TabStripPlacement" Value="Left">
                                    <Setter Property="Grid.Row" TargetName="headerPanel" Value="0"/>
                                    <Setter Property="Grid.Row" TargetName="contentPanel" Value="0"/>
                                    <Setter Property="Grid.Column" TargetName="headerPanel" Value="0"/>
                                    <Setter Property="Grid.Column" TargetName="contentPanel" Value="1"/>
                                    <Setter Property="Width" TargetName="ColumnDefinition0" Value="Auto"/>
                                    <Setter Property="Width" TargetName="ColumnDefinition1" Value="*"/>
                                    <Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
                                    <Setter Property="Height" TargetName="RowDefinition1" Value="0"/>
                                </Trigger>
                                <Trigger Property="TabStripPlacement" Value="Right">
                                    <Setter Property="Grid.Row" TargetName="headerPanel" Value="0"/>
                                    <Setter Property="Grid.Row" TargetName="contentPanel" Value="0"/>
                                    <Setter Property="Grid.Column" TargetName="headerPanel" Value="1"/>
                                    <Setter Property="Grid.Column" TargetName="contentPanel" Value="0"/>
                                    <Setter Property="Width" TargetName="ColumnDefinition0" Value="*"/>
                                    <Setter Property="Width" TargetName="ColumnDefinition1" Value="Auto"/>
                                    <Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
                                    <Setter Property="Height" TargetName="RowDefinition1" Value="0"/>
                                </Trigger>
                                <Trigger Property="IsEnabled" Value="false">
                                    <Setter Property="Effect" TargetName="templateRoot">
                                        <Setter.Value>
                                            <EffectLibrary:DesaturateEffect DesaturationFactor=".25"/>
                                        </Setter.Value>
                                    </Setter>
                                </Trigger>
                            </ControlTemplate.Triggers>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
            <Style x:Key="TabItemStyle" TargetType="{x:Type TabItem}">
                <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
                <Setter Property="Foreground" Value="{Binding Foreground, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type TabControl}}}"/>
                <Setter Property="Background" Value="{Binding Background, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type TabControl}}}"/>
                <Setter Property="BorderBrush" Value="{Binding BorderBrush, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type TabControl}}}"/>
                <Setter Property="Margin" Value="0"/>
                <Setter Property="Padding" Value="0,5"/>
                <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
                <Setter Property="VerticalContentAlignment" Value="Stretch"/>
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type TabItem}">
                            <Grid x:Name="templateRoot" SnapsToDevicePixels="true"  Background="{TemplateBinding Background}">
                                <Border x:Name="mainBorder" BorderBrush="{TemplateBinding BorderBrush}">
                                    <Border x:Name="highlightBorder"/>
                                </Border>
                                <ContentPresenter x:Name="contentPresenter" ContentSource="Header" Focusable="False" HorizontalAlignment="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
                            </Grid>
                            <ControlTemplate.Triggers>
                                <Trigger Property="IsEnabled" Value="false">
                                    <Setter Property="Effect" TargetName="templateRoot">
                                        <Setter.Value>
                                            <EffectLibrary:DesaturateEffect DesaturationFactor=".25"/>
                                        </Setter.Value>
                                    </Setter>
                                </Trigger>
                                <DataTrigger Binding="{Binding IsSelected, RelativeSource={RelativeSource Self}}" Value="true">
                                    <Setter TargetName="highlightBorder" Property="Background" Value="#0B79CE"/>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding TabStripPlacement, RelativeSource={RelativeSource AncestorType={x:Type TabControl}}}" Value="Top">
                                    <Setter TargetName="mainBorder" Property="BorderThickness" Value="0,0,1,0"/>
                                    <Setter TargetName="highlightBorder" Property="Height" Value="2"/>
                                    <Setter TargetName="highlightBorder" Property="VerticalAlignment" Value="Bottom"/>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding TabStripPlacement, RelativeSource={RelativeSource AncestorType={x:Type TabControl}}}" Value="Bottom">
                                    <Setter TargetName="mainBorder" Property="BorderThickness" Value="0,0,1,0"/>
                                    <Setter TargetName="highlightBorder" Property="Height" Value="2"/>
                                    <Setter TargetName="highlightBorder" Property="VerticalAlignment" Value="Top"/>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding TabStripPlacement, RelativeSource={RelativeSource AncestorType={x:Type TabControl}}}" Value="Left">
                                    <Setter TargetName="mainBorder" Property="BorderThickness" Value="0,0,0,1"/>
                                    <Setter TargetName="highlightBorder" Property="Width" Value="2"/>
                                    <Setter TargetName="highlightBorder" Property="HorizontalAlignment" Value="Right"/>
                                </DataTrigger>
                                <DataTrigger Binding="{Binding TabStripPlacement, RelativeSource={RelativeSource AncestorType={x:Type TabControl}}}" Value="Right">
                                    <Setter TargetName="mainBorder" Property="BorderThickness" Value="0,0,0,1"/>
                                    <Setter TargetName="highlightBorder" Property="Width" Value="2"/>
                                    <Setter TargetName="highlightBorder" Property="HorizontalAlignment" Value="Left"/>
                                </DataTrigger>
                            </ControlTemplate.Triggers>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </TabControl.Resources>
        <TabItem Header="Years">
            <ListBox Background="{DynamicResource Pallete.Primary.Brightest}" Foreground="{DynamicResource Pallete.Primary}">
                <TextBlock Text="2015"/>
                <TextBlock Text="2016"/>
                <TextBlock Text="2017"/>
            </ListBox>
        </TabItem>
        <TabItem Header="Tables">
            <ListBox  Background="{DynamicResource Pallete.Primary.Brightest}" Foreground="{DynamicResource Pallete.Primary}">
                <TextBlock Text="Table1..."/>
                <TextBlock Text="Table2..."/>
                <TextBlock Text="Table3..."/>
            </ListBox>
        </TabItem>
    </TabControl>
</Window>

Hope I've included all colors and it will work for you. Ahh... Snap! My Desaturation Effect! My WPF startup project you can grab that effect from there if you want (It's easier to plop the effect in trigger, than to recolor all the thing, same with highlights). Yes, that's a lot of code, but I simply changed ItemsContainer to look better and replaced standard Header control with UniformGrid and set Rows or Columns to 1 depending on TabStripPlacement. Now I can collapse this code, or hide it somewhere. :)

Conjoined

I've found a bad side of my effects. When I've highlighted Alternating items in TreeView, those items became blurry. So I made dedicated background Border that would have nothing in it, just behind an ItemPresenter, so it wouldn't be influenced by this effect. – Conjoined

Answer 9

I followed Charlie's suggestion and went on re-templating route. Here is a simple implementation of TabControl that divides available space equally among its TabItems, using UniformGrid:

Control's XAML

<TabControl x:Class="YourNamespace.Views.BigTabsTabControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:YourNamespace.Views"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300"
            Padding="2" HorizontalContentAlignment="Center" VerticalContentAlignment="Center"
            BorderThickness="1" Foreground="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}">

    <TabControl.Resources>
        <SolidColorBrush x:Key="TabItem.Selected.Background" Color="#FFFFFF"/>
        <SolidColorBrush x:Key="TabItem.Selected.Border" Color="#ACACAC"/>
    </TabControl.Resources>

    <TabControl.Style>
        <Style TargetType="{x:Type TabControl}">
            <Setter Property="Background" Value="{StaticResource TabItem.Selected.Background}"/>
            <Setter Property="BorderBrush" Value="{StaticResource TabItem.Selected.Border}"/>
        </Style>
    </TabControl.Style>

    <TabControl.Template>
        <ControlTemplate TargetType="{x:Type TabControl}">
            <Grid x:Name="templateRoot" ClipToBounds="true" SnapsToDevicePixels="true" KeyboardNavigation.TabNavigation="Local">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition x:Name="ColumnDefinition0"/>
                    <ColumnDefinition x:Name="ColumnDefinition1" Width="0"/>
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition x:Name="RowDefinition0" Height="Auto"/>
                    <RowDefinition x:Name="RowDefinition1" Height="*"/>
                </Grid.RowDefinitions>

                <UniformGrid x:Name="headerPanel" Background="Transparent" Grid.Column="0" IsItemsHost="true" Grid.Row="0" KeyboardNavigation.TabIndex="1" Panel.ZIndex="1" />
                <Border x:Name="contentPanel" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="0" KeyboardNavigation.DirectionalNavigation="Contained" Grid.Row="1" KeyboardNavigation.TabIndex="2" KeyboardNavigation.TabNavigation="Local">
                    <ContentPresenter x:Name="PART_SelectedContentHost" ContentSource="SelectedContent" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                </Border>
            </Grid>
            <ControlTemplate.Triggers>
                <Trigger Property="TabStripPlacement" Value="Bottom">
                    <Setter Property="Grid.Row" TargetName="headerPanel" Value="1"/>
                    <Setter Property="Grid.Row" TargetName="contentPanel" Value="0"/>
                    <Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
                    <Setter Property="Height" TargetName="RowDefinition1" Value="Auto"/>
                    <Setter Property="Margin" TargetName="headerPanel" Value="2,0,2,2"/>
                </Trigger>
                <Trigger Property="TabStripPlacement" Value="Left">
                    <Setter Property="Grid.Row" TargetName="headerPanel" Value="0"/>
                    <Setter Property="Grid.Row" TargetName="contentPanel" Value="0"/>
                    <Setter Property="Grid.Column" TargetName="headerPanel" Value="0"/>
                    <Setter Property="Grid.Column" TargetName="contentPanel" Value="1"/>
                    <Setter Property="Width" TargetName="ColumnDefinition0" Value="Auto"/>
                    <Setter Property="Width" TargetName="ColumnDefinition1" Value="*"/>
                    <Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
                    <Setter Property="Height" TargetName="RowDefinition1" Value="0"/>
                    <Setter Property="Margin" TargetName="headerPanel" Value="2,2,0,2"/>
                </Trigger>
                <Trigger Property="TabStripPlacement" Value="Right">
                    <Setter Property="Grid.Row" TargetName="headerPanel" Value="0"/>
                    <Setter Property="Grid.Row" TargetName="contentPanel" Value="0"/>
                    <Setter Property="Grid.Column" TargetName="headerPanel" Value="1"/>
                    <Setter Property="Grid.Column" TargetName="contentPanel" Value="0"/>
                    <Setter Property="Width" TargetName="ColumnDefinition0" Value="*"/>
                    <Setter Property="Width" TargetName="ColumnDefinition1" Value="Auto"/>
                    <Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
                    <Setter Property="Height" TargetName="RowDefinition1" Value="0"/>
                    <Setter Property="Margin" TargetName="headerPanel" Value="0,2,2,2"/>
                </Trigger>
                <Trigger Property="IsEnabled" Value="false">
                    <Setter Property="TextElement.Foreground" TargetName="templateRoot" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                </Trigger>
            </ControlTemplate.Triggers>
        </ControlTemplate>
    </TabControl.Template>
</TabControl>

Control's Code-Behind

using System.Windows.Controls;
using System.Windows.Controls.Primitives;

namespace YourNamespace.Views
{
  /// <summary>
  /// A TabControl with large tabs. 
  /// </summary>
  public partial class BigTabsTabControl : TabControl
  {
    public BigTabsTabControl()
    {
      InitializeComponent();
    }

    public override void OnApplyTemplate()
    {
      base.OnApplyTemplate();

      if (this.Template != null)
      {
        UniformGrid X = this.Template.FindName("headerPanel", this) as UniformGrid;
        if (X != null) X.Columns = this.Items.Count;
      }
    }
  }
}

That's it. You can now add TabItems to this control and they'll adjust their width automatically. No need to specify Grid.Column for these TabItems either, they work fine without it, even at design time.

Gradual

Why did you use margin to size the tabs, rather than setting RowDefinition0's height to a static number instead of 'Auto'? This makes no sense and is a backwards way of doing things. – Rozella

I'm not using margin to size the tabs.Tabs are automatically sized because of setting UniformGrid.Columns (that's what UniformGrid does). Also note that we can't set RowDefinition0's height to static number since user can use headers of any height. Lastly, in case you downvoted the answer, it is always kind and considerate to ask the OP if you don't understand something in an answer. – Gradual

From what I can tell, the opposite is true. The height of the tab content is static (300) and the height of the tab itself fills the rest of the available space. By setting RowDefinition0's Height property to 40, and removing the margin on UniformGrid, I was able to get the desired effect. Why is there a bottom margin of 300 on the UniformGrid? What purpose does that serve? Perhaps it's some funky interaction with the DockPanel I'm putting the tab in, and LastChildFill, but ultimately making those changes gave the desired effect, which leads me to believe it's how it should be. – Rozella

@AnthonyStivers: Thank you for pointing out. XAML actually had two issues. Firstly, the Margin setting shouldn't have been there; don't know how it made its way through. Secondly, Grid.Row should have been 0, not 1. Other than these two, rest of the things are correct and working absolutely fine for me. – Gradual

Ah yes, I think I had changed Grid.Row to 0 as well in my code. Setting RowDefinition0's height to Auto does work. In my case, I set it to 40 because I wanted a bit taller and more obvious tabs. I'm glad I was able to help improve the answer. – Rozella

To add to this answer, and feel free to edit it with this information, @dotNET. You will want to place this custom TabControl in a separate project within your solution. If you don't do so, when you attempt to add more than one tab to the TabControl, you may encounter a cryptic error The property 'content' can only be set once. At least in my case, I encountered this error, and it was resolved by placing the custom TabControl in its own project within the solution. The project still compiled fine and ran with the desired effect. It was only a design-time error. But annoying, nonetheless. – Rozella

Perhaps setting Height on the UniformGrid to 40 would be better than setting it on the RowDefinition, though. Both have the same effect, but setting it on UniformGrid is probably the better approach. – Rozella

Answer 10

I don't know if it will work for tabs, but whenever I've needed to stretch anything to fill a container I've used a ViewBox. Is that the kind of thing you're looking for?

Swec

Answer 11

In addition to Ryan Versaw's accepted solution which gives equal tabItem header widths, I found the following way to make it dependent on the length of each header.

First we get the string of each tabItem header by adding this line to the xaml multibinding. Thus it becomes:

<MultiBinding Converter="{StaticResource tabSizeConverter}">
           <Binding RelativeSource="{RelativeSource Mode=FindAncestor, AncestorType={x:Type TabControl}}" />
           <Binding RelativeSource="{RelativeSource Mode=FindAncestor, AncestorType={x:Type TabControl}}" Path="ActualWidth" />
           <Binding Path="Header" RelativeSource="{RelativeSource Self}"/>
</MultiBinding>

And a bit more of code in the Converter (values[] gets also the tabItem Header):

public object Convert(object[] values, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        TabControl tabControl = values[0] as TabControl;

        string AllHeaders = "";
        for (int i = 0; i < tabControl.Items.Count; i++)
        {
            int index = tabControl.Items[i].ToString().IndexOf("Header:") + "Header:".Length;
            string currentHeader = tabControl.Items[i].ToString().Substring(index);
            currentHeader = currentHeader.Substring(0, currentHeader.Length - " Content:".Length);
            AllHeaders += currentHeader;
        }

        //Normalize width according to header length
        double width = values[2].ToString().Length * tabControl.ActualWidth / AllHeaders.Length;

        //Subtract 1, otherwise we could overflow to two rows.
        var retVal = (width <= 1) ? 0 : (width - 1);
        return retVal;
    }

I suspect there might be a more efficient way to get the AllHeaders string of all the headers, but it works fine as it is ...

Lightface

Answer 12

I am using the following solution: In the main window i use a window re sized event and on tabcontrol Initialized event to set the Width of each Tab. The number '5' corresponds to my number of Tabs.

    private void tabchanger_Initialized(object sender, EventArgs e)
    {
        foreach (TabItem item in tabchanger.Items)
        {
            double newW = (tabchanger.ActualWidth / 5) - 1;
            if (newW < 0) newW = 0;

            item.Width = newW;
        }

    }

    private void Window_SizeChanged(object sender, SizeChangedEventArgs e)
    {
        foreach (TabItem item in tabchanger.Items)
        {
            double newW = (tabchanger.ActualWidth / 5) - 1;
            if (newW < 0) newW = 0;

            item.Width = newW;
        }
    }

Seclude