具有图像属性的WPF UserControl

Question

I have a UserControl Library containing a user control to make a custom title bar for windows. I have given this title bar two dependency properties - Title and Icon, which I would like to be able to set when I use the control through a DLL.

I have got the title working correctly, so that when I set a Title property of the Window's ViewModel, it is populated into the title bar. However, I cannot get the image to do the same.

I have tried all sorts of variations, and read an entire course on using dependency properties, but I just can't seem to get the image to show. I have tried using ImageSource properties, Project Resources, and Images, but all I get is a blank. Can you point me in the right direction to fix the issue?

Here is the xaml for the usercontrol (I Read that I had to use the TemplatedParent RelativeSource for the DP, so that is put in - I believe that this will refer to the MainViewModel in the implementation):

<UserControl x:Class="WPFLibrary.User_Controls.TitleBar"
             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">
    <UserControl.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/WPFLibrary;component/Styles/Buttons.xaml"/>
                <ResourceDictionary Source="pack://application:,,,/WPFLibrary;component/Styles/Gradients.xaml"/>
                <ResourceDictionary Source="pack://application:,,,/WPFLibrary;component/Styles/Text.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </UserControl.Resources>
    <DockPanel VerticalAlignment="Top" Grid.Row="0" Grid.ColumnSpan="3"
               MouseDown="TitleBar_MouseDown"
               DataContext="{Binding}"
               Background="{StaticResource WindowTitleBar}">
        <Grid Grid.Row="0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="5"/>
                <ColumnDefinition Width="30"/>
                <ColumnDefinition Width="5"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="90"/>
            </Grid.ColumnDefinitions>
            <Image Grid.Column="1" Source="{Binding Icon,RelativeSource={RelativeSource TemplatedParent}}"/>
            <TextBlock x:Name="Title_Bar"
                       Grid.Column="3"
                       Text="{Binding Title}"
                       Style="{StaticResource Text_WindowTitle}">
            </TextBlock>
            <!--StackPanel Containing the buttons excluded for SO Question-->
        </Grid>
    </DockPanel>
</UserControl>

and here is the code behind for the same control (Following from some other SO answers, I have tried using project resources and ImageSource for the Image property, but to no avail):

using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace WPFLibrary.User_Controls
{
    /// <summary>
    /// Interaction logic for TitleBar.xaml
    /// </summary>
    public partial class TitleBar : UserControl, INotifyPropertyChanged
    {

        public Image Icon
        {
            get { return (Image)GetValue(IconProperty); }
            set { SetValue(IconProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Icon.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty IconProperty = DependencyProperty.Register("Icon", typeof(Image), typeof(TitleBar) );

        private static PropertyChangedEventArgs _stateChange = new PropertyChangedEventArgs("Windowstate");
        public WindowState _windowState;

        public WindowState Windowstate
        {
            get
            { return _windowState; }
            set
            {
                _windowState = value;
                NotifyChange(_stateChange);
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        private void NotifyChange(PropertyChangedEventArgs e)
        {
            PropertyChanged?.Invoke(this, e);
        }

        public TitleBar()
        {
            InitializeComponent();
        }

        //Button Click Methods excluded for SO question
    }
}

The xaml for the implementation of the usercontrol is like this - I set the binding to the MainViewModel; that has a constructor that sets the properties.

<Window x:Class="Demo_of_WPF_Library.MainWindow"
        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:uc="clr-namespace:WPFLibrary.User_Controls;assembly=WPFLibrary"
        xmlns:vm="clr-namespace:Demo_of_WPF_Library.ViewModel"
        mc:Ignorable="d"
        WindowStyle="None"
        BorderBrush="{StaticResource WindowBackgroundBrush}"
        x:Name="Main_Window"
        WindowState="{Binding Windowstate,ElementName=Titlebar}"
        Background="{StaticResource WindowBackgroundBrush}"
        Height="300" Width="800">
    <Window.DataContext>
        <vm:MainView_Model/>
    </Window.DataContext>
    <Grid>
        <uc:TitleBar Name="Titlebar" Icon="{Binding Icon}">
        </uc:TitleBar>
    </Grid>
</Window>

Here is the code for the MainView_Model that holds the properties for the mainwindow:

namespace Demo_of_WPF_Library.ViewModel
{
    public class MainView_Model
    {
        private string _title;
        public string Title
        {
            get { return _title; }
            set { _title = value; }
        }
        private Image _icon;

        public Image Icon
        {
            get { return _icon; }
            set { _icon = value; }
        }

        public MainView_Model()
        {
            Title = "Demo WPF Library";
            Icon = new Image();
            Icon.Source = new BitmapImage(new Uri("/View/Images/IsItOk.ico",UriKind.Relative));
        }
    }
}

Finally, here is the code behind the mainwindow, which sets the binding to the MainViewModel and initialises the window:

public partial class MainWindow : Window
{
    public MainView_Model MainView { get; set; }
    public MainWindow()
    {
        MainView = new MainView_Model();
        DataContext = MainView;
        InitializeComponent();
    }
}

I honestly cannot see what it is that is missing / wrong here and I have read loads of articles, questions and answers that basically seem to say that I'm doing things in the correct way... So what on earth is wrong?

Answer 1

Your binding is wrong. You shouldn't use a TemplatedParent if you have no template. Use:

xmlns:local="clr-namespace:WPFLibrary.User_Controls"
<Image Grid.Column="1" Source="{Binding Icon, RelativeSource={RelativeSource AncestorType=local:TitleBar}}"/>

Answer 2

The problem is you've got an Image in your XAML which is trying to bind to an Image in your view model. GUI objects like Image have no place in your view model layer, change your Icon dependency property to be of type ImageSource and bind your XAML image to that instead.