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WPF Cannot make the passwordbox element corners rounded

I am trying to to get my PasswordBox corners rounded to make it look more modern. I have successfully done so with my button and TexBlock. However attempting to do so with my PasswordBox does not yield the same results that I desire.
The xaml code for the PasswordBox looks like this
<PasswordBox
Grid.Column="1"
Grid.Row="5"
x:Name="paswordinput"
Margin="170,0,0,0">
<PasswordBox.Resources>
<Style TargetType="Border">
<Setter Property="CornerRadius" Value="8"></Setter>
</Style>
</PasswordBox.Resources>
</PasswordBox>
the same code worked for my TextBox and my Button. Any help would greatly be appreciated!

The PasswordBox control clears the Style of the Border so you should set the local value of the CornerRadius property in the template:
<PasswordBox
Grid.Column="1"
Grid.Row="5"
x:Name="paswordinput"
Margin="170,0,0,0">
<PasswordBox.Style>
<Style TargetType="{x:Type PasswordBox}">
<Style.Resources>
<Style TargetType="Border">
<Setter Property="CornerRadius" Value="8" />
</Style>
</Style.Resources>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type PasswordBox}">
<Border x:Name="border" CornerRadius="8" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
<ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Opacity" TargetName="border" Value="0.56"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="#FF7EB4EA"/>
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="#FF569DE5"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsInactiveSelectionHighlightEnabled" Value="true"/>
<Condition Property="IsSelectionActive" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="SelectionBrush" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightBrushKey}}"/>
</MultiTrigger>
</Style.Triggers>
</Style>
</PasswordBox.Style>
</PasswordBox>

Hope this blog post will help - https://www.kailashsblogs.com/2017/01/round-corner-passwordbox-in-wpf.html
Use the below code -
<PasswordBox Margin="10" Height="50" Width="200">
<PasswordBox.Template>
<ControlTemplate TargetType="PasswordBox">
<Border CornerRadius="10" BorderBrush="Gray" BorderThickness="1" />
</ControlTemplate>
</PasswordBox.Template>
</PasswordBox>

You could also try to use the following code to set rounded corners for Password. For more details, please refer to here.
<PasswordBox x:Name="paswordinput" Width="100" Height="50">
<PasswordBox.Resources>
<Style TargetType="PasswordBox">
<Setter Property="Template" >
<Setter.Value>
<ControlTemplate>
<Border CornerRadius="10" BorderBrush="Gray" BorderThickness="2" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</PasswordBox.Resources>
</PasswordBox>

Treeview Toggle Button Style working only for Parent Node and not for Child Nodes

I have a treeview, for which I wrote the style template of treeview in App.xaml, as I need to apply the style in two or three treeviews in my application. Now my problem is that the togglebutton style works for parent and not for child nodes.
Here for the togglebutton collapse and expand, i added two images(
Resources/Images/arrowexpand.png
and
Resources/Images/arrowcollapse.png
It is working perfectly with parent nodes, but not with child and subchild nodes.
For the child and subchild nodes, the default triangle button comes.
I didn't use MVVM. I don't know where I am going wrong
In the treeview
<TreeView x:Name="myTreeview" ItemContainerStyle="{StaticResource ms}"/>
Here is my code in App.xaml
<Style TargetType="TreeView">
<Setter Property="OverridesDefaultStyle" Value="True"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TreeView">
<Border Name="Border" CornerRadius="5" BorderThickness="2">
<Border.BorderBrush>
<SolidColorBrush Color="DarkGreen"/>
</Border.BorderBrush>
<ItemsPresenter/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="ExpandCollapseToggleStyle" TargetType="ToggleButton">
<Setter Property="Focusable" Value="False"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ToggleButton">
<Image x:Name="image" Source="Resources/Images/arrowcollapse.png" />
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="true">
<Setter TargetName="image" Property="Source" Value="Resources/Images/arrowexpand.png" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="ms" TargetType="TreeViewItem" >
<Setter Property="IsExpanded" Value="True"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Padding" Value="1,0,0,0"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TreeViewItem">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="19" Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition/>
</Grid.RowDefinitions>
<!-- Connecting Lines -->
<Rectangle x:Name="HorLn" Margin="9,1,0,0" Height="1" Stroke="#DCDCDC" SnapsToDevicePixels="True"/>
<Rectangle x:Name="VerLn" Width="1" Stroke="#DCDCDC" Margin="0,0,1,0" Grid.RowSpan="2" SnapsToDevicePixels="true" Fill="White"/>
<ToggleButton Margin="-1,0,0,0" x:Name="Expander" Style="{StaticResource ExpandCollapseToggleStyle}" IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press"/>
<ToggleButton Margin="-1,0,0,0" x:Name="Collapsed" Style="{StaticResource ExpandCollapseToggleStyle}" IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press"/>
<Border Name="Bd" Grid.Column="1" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
<ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" MinWidth="20"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="2"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="False">
<Setter TargetName="ItemsHost" Property="Visibility" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter TargetName="Expander" Property="Visibility" Value="Hidden"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasHeader" Value="false"/>
<Condition Property="Width" Value="Auto"/>
</MultiTrigger.Conditions>
<Setter TargetName="PART_Header" Property="MinWidth" Value="75"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasHeader" Value="false"/>
<Condition Property="Height" Value="Auto"/>
</MultiTrigger.Conditions>
<Setter TargetName="PART_Header" Property="MinHeight" Value="19"/>
</MultiTrigger>
<Trigger Property="IsSelected" Value="true">
<Setter TargetName="Bd" Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="true"/>
<Condition Property="IsSelectionActive" Value="false"/>
</MultiTrigger.Conditions>
<Setter TargetName="Bd" Property="Background" Value="Green"/>
<Setter Property="Foreground" Value="White"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I want the arrow button to be for the child items and subchild items. Please tell me where I am wrong

I found out the Solution. Actually I am trying to apply the styles for the derived classes of the treeview item. So only my style was not working.
What I did was I just added this style statement in my Constructor of the derived Class
Style = (Style)FindResource(typeof(TreeViewItem));
Then the style was applied to all the items in the treeview.

Wrong hover effect on the child elements of a WPF TreeView

I would like to ask you an issue that I cannot solve. I have templated a WPF TreeView as follows:
<Style x:Key="TreeViewItemStyle" TargetType="{x:Type TreeViewItem}">
<Setter Property="Focusable"
Value="True" />
<Setter Property="IsExpanded"
Value="True" />
<Setter Property="Background"
Value="Transparent" />
<Setter Property="HorizontalContentAlignment"
Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment"
Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="HorizontalAlignment"
Value="Stretch" />
<Setter Property="Width"
Value="{Binding Path=ActualWidth, RelativeSource={RelativeSource AncestorType={x:Type TreeView}}}" />
<Setter Property="Foreground"
Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Grid Name="PART_grid">
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="19" Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition/>
</Grid.RowDefinitions>
<ToggleButton x:Name="Expander"
ClickMode="Press"
IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}"
Style="{StaticResource ExpandCollapseToggleStyle}"/>
<Border x:Name="Bd"
Grid.Column="1"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
Background="{TemplateBinding Background}"
Padding="{TemplateBinding Padding}"
SnapsToDevicePixels="true">
<ContentPresenter x:Name="PART_Header"
ContentSource="Header"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.Row="1" Grid.Column="1" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="false">
<Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Cursor" Value="Hand" />
<Setter TargetName="PART_grid"
Property="Background"
Value="#e6f2fa" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
The problem is that the hover effect is really terrible. In fact, if the user goes on the TreeviewItem the effect should affect only the relative children and not the whole wrapper.
How can I solve this problem and make the hover effect fall only on the single element, parent or child?
Thank you so much and have a good day everyone

I suppose you are using the HierarchicalDataTemplate for your items.
In that case, the 'terrible' hover effect is actually working exactly as you specify it. E.g. the Sergio item will contain other sub-items. When you hover on Alessandro, the Sergio item actually contains the mouse too, because this Sergio item is that large and contains all the other sub-items, including Alessandro.
You have two options now.
Either do it in your data template, something like:
<HierarchicalDataTemplate ItemsSource="{Binding SubItems}">
<TextBlock x:Name="HeaderText" Text="{Binding Name}"/>
<HierarchicalDataTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="HeaderText" Property="Background" Value="Red"/>
</Trigger>
</HierarchicalDataTemplate.Triggers>
</HierarchicalDataTemplate>
Or set the color not on the grid, but on the header only:
<Trigger Property="IsMouseOver" Value="true" SourceName="Bd">
<Setter Property="Cursor" Value="Hand" />
<Setter TargetName="Bd" Property="Background" Value="#e6f2fa" />
</Trigger>
Note that I added SourceName="Bd" to the trigger: we only want to change the color when the corresponding header contains the mouse cursor.

Adjust dropdown arrow margin of WPF TreeView

I have a TreeView which simplified is defined as
<TreeView ItemsSource="{Binding TreeItems}">
<TreeView.Resources>
<DataTemplate DataType="{x:Type models:MyModel}">
<Border Margin="{Binding Margin}" >
<Grid>
<TextBlock Text="{Binding Path=Name}" Margin="3,3,3,3" />
</Grid>
</Border>
</DataTemplate>
</TreeView.Resources>
</TreeView>
It looks like this
As you can see due to the Margin, which is variable, there is space between the items. The problem is the dropdown arrow. It is not centered on the element. Well, it is centered on the element ignoring the margin. How do I adjust the arrow?

Your XAML markup is both incomplete and incorrect: the DataTemplate should be a HierarchicalDataTemplate and it should be placed in a <TreeView.ItemTemplate> tag. This doesn't apply after your edit.
You can apply the margin to the complete TreeViewItem content including the dropdown arrow:
<TreeView ItemsSource="{Binding Items}">
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="Margin" Value="{Binding Margin}"/>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding SubItems}">
<Border>
<Grid>
<TextBlock Margin="3,3,3,3"/>
</Grid>
</Border>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>

Yes, I know the style below is too lengthy, but give it a try.
Just put it in a separate resource dictionary and merge it.
<TreeView ItemsSource="{Binding TreeItems}" ItemContainerStyle="{StaticResource CenteredExpanderTreeViewItemStyle}">
<TreeView.Resources>
<DataTemplate DataType="{x:Type models:MyModel}">
<Border Margin="{Binding Margin}" >
<Grid>
<TextBlock Text="{Binding Path=Name}" Margin="3,3,3,3" />
</Grid>
</Border>
</DataTemplate>
</TreeView.Resources>
</TreeView>
CenteredExpanderTreeViewItemStyle.xaml
<Style x:Key="TreeViewItemFocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Checked.Fill" Color="#FF595959"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Checked.Stroke" Color="#FF262626"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Stroke" Color="#FF27C7F7"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Fill" Color="#FFCCEEFB"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Checked.Stroke" Color="#FF1CC4F7"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Checked.Fill" Color="#FF82DFFB"/>
<PathGeometry x:Key="TreeArrow" Figures="M0,0 L0,6 L6,0 z"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Fill" Color="#FFFFFFFF"/>
<SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Stroke" Color="#FF818181"/>
<Style x:Key="ExpandCollapseToggleStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Focusable" Value="False"/>
<Setter Property="Width" Value="16"/>
<Setter Property="Height" Value="16"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Background="Transparent" Height="16" Padding="5,5,5,5" Width="16">
<Path x:Name="ExpandPath" Data="{StaticResource TreeArrow}" Fill="{StaticResource TreeViewItem.TreeArrow.Static.Fill}" Stroke="{StaticResource TreeViewItem.TreeArrow.Static.Stroke}">
<Path.RenderTransform>
<RotateTransform Angle="135" CenterY="3" CenterX="3"/>
</Path.RenderTransform>
</Path>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="True">
<Setter Property="RenderTransform" TargetName="ExpandPath">
<Setter.Value>
<RotateTransform Angle="180" CenterY="3" CenterX="3"/>
</Setter.Value>
</Setter>
<Setter Property="Fill" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.Static.Checked.Fill}"/>
<Setter Property="Stroke" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.Static.Checked.Stroke}"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Stroke" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Stroke}"/>
<Setter Property="Fill" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Fill}"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
<Condition Property="IsChecked" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Stroke" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Checked.Stroke}"/>
<Setter Property="Fill" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Checked.Fill}"/>
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="CenteredExpanderTreeViewItemStyle" TargetType="{x:Type TreeViewItem}">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Padding" Value="1,0,0,0"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="19" Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition/>
</Grid.RowDefinitions>
<ToggleButton x:Name="Expander" VerticalAlignment="Center" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource ExpandCollapseToggleStyle}"/>
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
<ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="false">
<Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="true"/>
<Condition Property="IsSelectionActive" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="VirtualizingPanel.IsVirtualizing" Value="true">
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<VirtualizingStackPanel/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>

Use given style for TreeViewItem like give below
<Style TargetType="TreeViewItem" BasedOn="{StaticResource {x:Type TreeViewItem}}">
<Setter Property="Margin" Value="3,3,3,3"></Setter>
</Style>
Hope this help.

To add a margin to the ToggleButton in a TreeView, you have to add a custom ControlTemplate. There are several good tutorials on MSDN, for example here: https://msdn.microsoft.com/de-de/library/ms788727(v=vs.85).aspx
I stripped one example down to the necessary elements to match your requirements. Please note, that the ToggleButton is this example is not styled at all, so it appears a normal Button would do. But I am sure, you find several good examples on how to style this Button in a way that suites you the best.
The code:
<Window.Resources>
<Style x:Key="TreeViewItemStyle" TargetType="{x:Type TreeViewItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Grid Margin="{Binding Margin}">
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="20" Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<ToggleButton Grid.Column="0" x:Name="Expander" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" />
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Row="0" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
<ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1" Margin="-10,0,0,0"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="false">
<Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="true"/>
<Condition Property="IsSelectionActive" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="VirtualizingStackPanel.IsVirtualizing" Value="true">
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<VirtualizingStackPanel/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<TreeView ItemsSource="{Binding TreeItems}" ItemContainerStyle="{StaticResource TreeViewItemStyle}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type library:MyModel}" ItemsSource="{Binding Children}" >
<TextBlock Text="{Binding Name}"></TextBlock>
</HierarchicalDataTemplate>
</TreeView.Resources>
</TreeView>

You should be able to do just this:
<Style TargetType="{x:Type TreeViewItem}" BasedOn="{StaticResource {x:Type TreeViewItem}}">
<Setter Property="Margin" Value="0,0,0,0" />
<!--Or edit Padding if Margin doesn't work-->
</Style>
It will use default style of a TreeViewItem and edit only defined properties. If you use explicitly defined style for TreeViewItem, use BaseOn="{StaticResource [YourStyleKey]}" (without [ ]).
If you need some more advanced styling I'd suggest you to use Blend to get the ControlTemplate of a TreeViewItem, then just edit it to your needs, without changing too much (keep in mind that names of controls used as a template may have a crucial meaning, so be careful what you are editing).
If you don't know how to use Blend to get your control's template, here is a simple tutorial described in a documentation of Telerik controls (don't worry, it works the same for all controls). You just need to create copy of a TreeViewItem ControlTemplate, paste it to your application and you are good to go (editing).
By using Blend you can get templates of all building blocks of a TreeView control and make them look like you want them to. You just need to do some digging.

How can I get an inset drop shadow using WPF XAML

I've tried following a few different answers here on SO on achieving a drop shadow effect on my Textbox, here is the code I have so far:
<Style x:Key="TextBoxRoundedInset" TargetType="{x:Type TextBox}">
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"/>
<Setter Property="BorderBrush" Value="{StaticResource TextBox.Static.Border}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="KeyboardNavigation.TabNavigation" Value="None"/>
<Setter Property="HorizontalContentAlignment" Value="Left"/>
<Setter Property="FocusVisualStyle" Value="{x:Null}"/>
<Setter Property="AllowDrop" Value="true"/>
<Setter Property="ScrollViewer.PanningMode" Value="VerticalFirst"/>
<Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
<Setter Property="TextAlignment" Value="Center"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Border x:Name="border" CornerRadius="3" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True" ClipToBounds="True">
<Border Background="Transparent" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Margin="-2">
<ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
<Border.Effect>
<DropShadowEffect ShadowDepth="0" BlurRadius="10"/>
</Border.Effect>
</Border>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Opacity" TargetName="border" Value="0.56"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource TextBox.MouseOver.Border}"/>
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource TextBox.Focus.Border}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsInactiveSelectionHighlightEnabled" Value="true"/>
<Condition Property="IsSelectionActive" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="SelectionBrush" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightBrushKey}}"/>
</MultiTrigger>
</Style.Triggers>
</Style>
Then to display with the styling I have
<TextBox x:Name="textBox" Background="#263238" Height="40" Margin="0,0,0,50" TextWrapping="Wrap" Width="221" VerticalAlignment="Center" HorizontalAlignment="Center" BorderThickness="0" Style="{DynamicResource TextBoxRoundedInset}" FontSize="25"/>
But I end up with a result that looks like this:
I don't want the text to have a glow to it, instead I basically want the text field to look like its dropped into the background any information on how to correct this would be great thanks

I usually use the BorderThickness Property in combination with the BorderBrush Property to give that 3D effect to make it look as if the field is pressed inside, or even outside by swapping the values of the BorderThickness of both Borders.
This is what I used with your snipped:
<Border x:Name="border" CornerRadius="3" BorderBrush="White" BorderThickness="0,0,2,2" Background="{TemplateBinding Background}" SnapsToDevicePixels="True" ClipToBounds="True">
<Border Background="Transparent" BorderBrush="Black" BorderThickness="2,2,0,0" CornerRadius="2">
<ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
</Border>
</Border>
The disadvantage is not being able to change the BorderBrush and BorderThickness Property anymore since they have no Binding.
Just change the colors in those two Borders to fit your need, I usually just use Black and White since that combination usually gives the strongest effect.

Old question but I did this a little differently. The effect looks less harsh, depending on chosen BorderBrush and BorderThickness.
<Border Background="Transparent" BorderThickness="2" BorderBrush="Black">
<Border.Effect>
<BlurEffect/>
</Border.Effect>
<ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
</Border>
The result can look like
this