Rounded corner of RichTextBox in wpf

Question

Maybe RichTextBox has an angular radius in wpf. I know this can be achieved with a ControlTemplate, but how?

I hope some of you can give me a hint.

Answer 1

How about placing a border around it?

 <Border BorderThickness="2" CornerRadius="6">
 <your:RichTextBox />
 </Border>

Answer 2

I tried Klau's suggestion and it didn't work for me, so I came up with something by itself:

<Window.Resources>
    <LinearGradientBrush x:Key="TextBoxBorder" EndPoint="0,20" MappingMode="Absolute" StartPoint="0,0">
        <GradientStop Color="#ABADB3" Offset="0.05"/>
        <GradientStop Color="#E2E3EA" Offset="0.07"/>
        <GradientStop Color="#E3E9EF" Offset="1"/>
    </LinearGradientBrush>
    <Style x:Key="{x:Type TextBoxBase}" BasedOn="{x:Null}" TargetType="{x:Type TextBoxBase}">
        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
        <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"/>
        <Setter Property="BorderBrush" Value="{StaticResource TextBoxBorder}"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="Padding" Value="1"/>
        <Setter Property="AllowDrop" Value="true"/>
        <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
        <Setter Property="ScrollViewer.PanningMode" Value="VerticalFirst"/>
        <Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBoxBase}">
                    <Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" Background="{TemplateBinding Background}"  SnapsToDevicePixels="true" CornerRadius="20" BorderThickness="9,6,10,7">
                        <ScrollViewer x:Name="PART_ContentHost" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style x:Key="{x:Type Hyperlink}" TargetType="{x:Type Hyperlink}">
        <Setter Property="Foreground" Value="Blue"/>
        <Setter Property="TextDecorations" Value="Underline"/>
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="true">
                <Setter Property="Foreground" Value="Red"/>
            </Trigger>
            <Trigger Property="IsEnabled" Value="false">
                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
            </Trigger>
            <Trigger Property="IsEnabled" Value="true">
                <Setter Property="Cursor" Value="Hand"/>
            </Trigger>
        </Style.Triggers>
    </Style>
    <Style x:Key="RichTextBoxWithRoundedCorners" TargetType="{x:Type RichTextBox}">
        <Style.Resources>
            <Style x:Key="{x:Type FlowDocument}" TargetType="{x:Type FlowDocument}">
                <Setter Property="OverridesDefaultStyle" Value="true"/>
            </Style>
            <Style x:Key="{x:Type Hyperlink}" BasedOn="{StaticResource {x:Type Hyperlink}}" TargetType="{x:Type Hyperlink}">
                <Style.Triggers>
                    <Trigger Property="IsMouseOver" Value="true">
                        <Setter Property="Foreground" Value="Blue"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                    </Trigger>
                </Style.Triggers>
            </Style>
        </Style.Resources>
        <Setter Property="MinWidth" Value="10"/>
        <Style.BasedOn>
            <StaticResource ResourceKey="{x:Type TextBoxBase}"/>
        </Style.BasedOn>
    </Style>
</Window.Resources>

I replaced the default RichTextBoxe border with the Border class, and this time it works:

<RichTextBox Background="White" Margin="75,0,114,94" Height="125" VerticalAlignment="Bottom" Style="{StaticResource RichTextBoxWithRoundedCorners}"  />

And picture:

You can probably do it better, but it's a good start.