TextBox with password & placeholder

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.Media;

namespace Dubsmash.Controls
{
    public class PlatformTextBox : TextBox
    {
        private ContentControl PlaceholderElement;

        public PlatformTextBox()
        {
            DefaultStyleKey = typeof(PlatformTextBox);

            TextChanged += OnTextChanged;
        }

        public override void OnApplyTemplate()
        {
            PlaceholderElement = (ContentControl)GetTemplateChild("PlaceholderElement");
            DeterminePlaceholderElementVisibility();

            base.OnApplyTemplate();
        }

        private void DeterminePlaceholderElementVisibility()
        {
            if (string.IsNullOrEmpty(this.Text))
            {
                PlaceholderElement.Visibility = Visibility.Visible;
            }
            else
            {
                PlaceholderElement.Visibility = Visibility.Collapsed;
            }
        }

        private void OnTextChanged(object sender, TextChangedEventArgs e)
        {
            var binding = this.GetBindingExpression(TextBox.TextProperty);
            if (binding != null)
                binding.UpdateSource();

            DeterminePlaceholderElementVisibility();
        }

        #region PlaceholderText
        public string PlaceholderText
        {
            get { return (string)GetValue(PlaceholderTextProperty); }
            set { SetValue(PlaceholderTextProperty, value); }
        }

        public static readonly DependencyProperty PlaceholderTextProperty =
            DependencyProperty.Register("PlaceholderText", typeof(string), typeof(PlatformTextBox), new PropertyMetadata(string.Empty));
        #endregion

        #region IsPassword
        public bool IsPassword
        {
            get { return (bool)GetValue(IsPasswordProperty); }
            set { SetValue(IsPasswordProperty, value); }
        }

        public static readonly DependencyProperty IsPasswordProperty =
            DependencyProperty.Register("IsPassword", typeof(bool), typeof(PlatformTextBox), new PropertyMetadata(false, OnIsPasswordChanged));

        private static void OnIsPasswordChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if((bool)e.NewValue)
            {
                (d as PlatformTextBox).FontFamily = new FontFamily("/Assets/Fonts/password.ttf#Password");
            }
            else
            {
                (d as PlatformTextBox).FontFamily = (FontFamily)App.Current.Resources["PhoneFontFamilyNormal"];
            }
        }
        #endregion
    }
}










<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:Dubsmash.Controls">

    <Style TargetType="local:PlatformTextBox">
        <Setter Property="FontFamily" Value="{StaticResource PhoneFontFamilyNormal}"/>
        <Setter Property="FontSize" Value="{StaticResource PhoneFontSizeMediumLarge}"/>
        <Setter Property="Background" Value="{StaticResource PhoneTextBoxBrush}"/>
        <Setter Property="Foreground" Value="{StaticResource PhoneTextBoxForegroundBrush}"/>
        <Setter Property="BorderBrush" Value="{StaticResource PhoneTextBoxBrush}"/>
        <Setter Property="SelectionBackground" Value="{StaticResource PhoneAccentBrush}"/>
        <Setter Property="SelectionForeground" Value="{StaticResource PhoneTextBoxSelectionForegroundBrush}"/>
        <Setter Property="BorderThickness" Value="{StaticResource PhoneBorderThickness}"/>
        <Setter Property="Padding" Value="2"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:PlatformTextBox">
                    <Grid Background="Transparent">
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal"/>
                                <VisualState x:Name="MouseOver"/>
                                <VisualState x:Name="Disabled">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="MainBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="Transparent"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="MainBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneDisabledBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneDisabledBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="ReadOnly">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="MainBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Collapsed</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ReadonlyBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Visible</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="ReadonlyBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneTextBoxBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="ReadonlyBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneTextBoxBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneTextBoxReadOnlyBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="FocusStates">
                                <VisualState x:Name="Focused">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="MainBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneTextBoxEditBackgroundBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="MainBorder">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneTextBoxEditBorderBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Unfocused"/>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="MainBorder" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Margin="{StaticResource PhoneTouchTargetOverhang}"/>
                        <Border x:Name="ReadonlyBorder" BorderBrush="{StaticResource PhoneDisabledBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="Transparent" Margin="{StaticResource PhoneTouchTargetOverhang}" Visibility="Collapsed"/>
                        <Border BorderBrush="Transparent" BorderThickness="{TemplateBinding BorderThickness}" Background="Transparent" Margin="{StaticResource PhoneTouchTargetOverhang}">
                            <ContentControl x:Name="PlaceholderElement" Content="{TemplateBinding PlaceholderText}" Foreground="{StaticResource PhoneDisabledBrush}" FontFamily="{StaticResource PhoneFontFamilyNormal}" BorderThickness="0" HorizontalContentAlignment="Stretch" Margin="{StaticResource PhoneTextBoxInnerMargin}" Padding="{TemplateBinding Padding}" VerticalContentAlignment="Stretch"/>
                        </Border>
                        <Border BorderBrush="Transparent" BorderThickness="{TemplateBinding BorderThickness}" Background="Transparent" Margin="{StaticResource PhoneTouchTargetOverhang}">
                            <ContentControl x:Name="ContentElement" BorderThickness="0" HorizontalContentAlignment="Stretch" Margin="{StaticResource PhoneTextBoxInnerMargin}" Padding="{TemplateBinding Padding}" VerticalContentAlignment="Stretch"/>
                        </Border>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>