Question

I have a User Control Library that I am loading dynamically. From that lib I am inserting a Tabitem into a TabControl. I can load the tab and show it without error. However, I can’t seem to get the binding on the control working.

This is the code I use to load it and add it to the TabControl:

    Assembly moduleAssembly = Assembly.Load("ControlLib");            
    UserControl uc = (UserControl)Application.LoadComponent(new System.Uri("/ControlLib;component/UserControl1.xaml", UriKind.RelativeOrAbsolute));
    TabControl itemsTab = (TabControl)this.FindName("mainTabControl");
    TabItem newTab = new TabItem();
    newTab.Content = uc;
    newTab.Header = "Test";
    itemsTab.Items.Add(newTab);
    itemsTab.SelectedItem = newTab;

This is the C# code for the control:

public partial class UserControl1 : UserControl
{        
    public static readonly DependencyProperty TestStringProperty = 
        DependencyProperty.Register("TestString", typeof(string), typeof(UserControl1));

    public string TestString { get; set; }

    public UserControl1()
    {
        InitializeComponent();

        TestString = "Hello World";
    }
}

This is the XAML code for the control:

<UserControl x:Class="ControlLib.UserControl1"
             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="300" d:DesignWidth="300">
    <Grid>        
        <TextBox Height="30" Width="100" HorizontalAlignment="Left" VerticalAlignment="Bottom" Text="{Binding Path=TestString, Mode=TwoWay}" />
    </Grid>
</UserControl>

When the tab displays all I see if a blank in the TextBox rather than “Hello World”

What am I missing?

Answer 1

You would still be setting the DataContext of your user control to instance of the class. Just how you go about creating that instance differs as you would be loading that dll a runtime. But fundamentally the binding setup remains the same.

    var assembly = Assembly.LoadFrom(@"yourdllname.dll");
    Type type = assembly.GetType("ClassLibrary1.SampleViewModel"); 
    object instanceOfMyType = Activator.CreateInstance(type);

    DataContext = instanceOfMyType;

For how basic databinding works read MSDN documentation.

Make sure you select the correct framework on the top of the screen.

EDIT

Usually this is created as a separate class (ViewModel in MVVM pattern).

 public partial class Window3 : Window, INotifyPropertyChanged
    {
        public Window3()
        {
            InitializeComponent();

            DataContext = this;
            TestString = "Hello World.";
        }

        string _testString;
        ///<summary>Gets or sets TestString.</summary>            
        public string TestString
        {
            get { return _testString; }
            set { _testString = value; OnPropertyChanged("TestString"); }
        }



        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                var e = new PropertyChangedEventArgs(propertyName);
                PropertyChanged(this, e);
            }
        }
    }