title: XAML editor just keeps showing: The member is not recognized or is not accessible
body: <p>I created an UserControl: A TextBox that shows an icon on the left side. My code seems to work but the following error keeps showing and makes the XAML editor mark it as an error.</p>
  
  <blockquote>
    <p>The member is not recognized or is not accessible.</p>
  </blockquote>
  
  <p>I also don't get autocompletion inside my properties at all, I assume it is because of the error? I'm not that familiar with WPF UserControls.</p>
  
  <p>I have already cleaned and rebuilt / restarted my project multiple times. That didn't help, the XAML editor just keeps showing this error on every custom property.</p>
  
  <p>I'm using .NET 4.6.1.</p>
  
  <p>LoginWindow.xaml:</p>
  
  <pre><code>&lt;Window x:Class="SMSBrowser.LoginWindow"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:control="clr-namespace:SMSBrowser.Controls"
      Title="SMS Browser - Login" SizeToContent="WidthAndHeight" ResizeMode="NoResize" Background="DimGray"&gt;
  &lt;Grid&gt;
      &lt;StackPanel Margin="30" HorizontalAlignment="Center" VerticalAlignment="Center"&gt;
          &lt;TextBlock Text="Test" TextAlignment="Center" FontSize="32" FontWeight="Bold" Foreground="White" Margin="0,0,0,25" /&gt;
          &lt;control:IconTextBox CustomBackground="Yellow" CustomIconSource="..\Resources\Icons\User.ico" Height="25" Margin="0,0,0,4" /&gt;
          &lt;control:IconTextBox CustomBackground="Red" CustomIconSource="..\Resources\Icons\Key.ico" Height="25" Margin="0,4,0,4" /&gt;
          &lt;Button Content="Login" Height="25" Width="400" Margin="0,4,0,0" /&gt;
      &lt;/StackPanel&gt;
  &lt;/Grid&gt;
  </code></pre>
  
  <p></p>
  
  <p>IconTextBox.xaml</p>
  
  <pre><code>&lt;UserControl x:Class="SMSBrowser.Controls.IconTextBox"
           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"
           mc:Ignorable="d"
           d:DesignHeight="25" d:DesignWidth="300"
           x:Name="LayoutRoot"&gt;
  &lt;Border BorderBrush="{Binding Path=CustomBorderBrush, ElementName=LayoutRoot}" BorderThickness="{Binding Path=CustomBorderThickness, ElementName=LayoutRoot}"&gt;
      &lt;DockPanel Background="{Binding Path=CustomBackground, ElementName=LayoutRoot}"&gt;
          &lt;Image Source="{Binding Path=CustomIconSource, ElementName=LayoutRoot}" Margin="{Binding Path=CustomIconMargin, ElementName=LayoutRoot}" DockPanel.Dock="Left" /&gt;
          &lt;TextBox Text="{Binding Path=CustomText, ElementName=LayoutRoot}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" VerticalContentAlignment="Center" BorderThickness="0" /&gt;
      &lt;/DockPanel&gt;
  &lt;/Border&gt;
  </code></pre>
  
  <p></p>
  
  <p>IconTextBox.cs</p>
  
  <pre><code>namespace SMSBrowser.Controls
  {
  /// &lt;summary&gt;
  /// Interaction logic for IconTextBox.xaml
  /// &lt;/summary&gt;
  public partial class IconTextBox : UserControl
  {
      public IconTextBox()
      {
          InitializeComponent();
          DataContext = LayoutRoot;
      }
  
      public string CustomBackground
      {
          get { return (string)GetValue(CustomBackgroundProperty); }
          set { SetValue(CustomBackgroundProperty, value); }
      }
  
      public static readonly DependencyProperty CustomBackgroundProperty =
          DependencyProperty.Register("CustomBackground", typeof(string), typeof(IconTextBox));
  
      public string CustomBorderBrush
      {
          get { return (string)GetValue(CustomBorderBrushProperty); }
          set { SetValue(CustomBorderBrushProperty, value); }
      }
  
      public static readonly DependencyProperty CustomBorderBrushProperty =
          DependencyProperty.Register("CustomBorderBrush", typeof(string), typeof(IconTextBox), new PropertyMetadata(""));
  
      public string CustomBorderThickness
      {
          get { return (string)GetValue(CustomBorderThicknessProperty); }
          set { SetValue(CustomBorderThicknessProperty, value); }
      }
  
      public static readonly DependencyProperty CustomBorderThicknessProperty =
          DependencyProperty.Register("CustomBorderThickness", typeof(string), typeof(IconTextBox), new PropertyMetadata(""));
  
      public string CustomIconMargin
      {
          get { return (string)GetValue(CustomIconMarginProperty); }
          set { SetValue(CustomIconMarginProperty, value); }
      }
  
      public static readonly DependencyProperty CustomIconMarginProperty =
          DependencyProperty.Register("CustomIconMargin", typeof(string), typeof(IconTextBox), new PropertyMetadata(""));
  
      public string CustomIconSource
      {
          get { return (string)GetValue(CustomIconSourceProperty); }
          set { SetValue(CustomIconSourceProperty, value); }
      }
  
      public static readonly DependencyProperty CustomIconSourceProperty =
          DependencyProperty.Register("CustomIconSource", typeof(string), typeof(IconTextBox), new PropertyMetadata(""));
  
      public string CustomText
      {
          get { return (string)GetValue(CustomTextProperty); }
          set { SetValue(CustomTextProperty, value); }
      }
  
      public static readonly DependencyProperty CustomTextProperty =
          DependencyProperty.Register("CustomText", typeof(string), typeof(IconTextBox), new PropertyMetadata(""));
  }
  }
  </code></pre>
  
  <p>Screenshot:</p>
  
  <p><a href="https://i.stack.imgur.com/cQqx1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cQqx1.png" alt="Errors"></a></p>