How to set ItemsPanelTemplate to a dynamically created Grid in code behind

Question

I\'ve got this UserControl defined in XAML and would like to set the ItemsPanelTemplate dynamically in my code behind class (not in th

Answer 1

Here's a XAML based program which uses ItemsPanelTemplate with a Grid:

MainWindow.xaml:

MainWindow.xaml.cs:

using System.Windows;

namespace WpfTutorialStatusBarGrid
{
    /// 

    /// Interaction logic for MainWindow.xaml
    /// 
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void TxtEditor_SelectionChanged(object sender, RoutedEventArgs e)
        {
            var row = txtEditor.GetLineIndexFromCharacterIndex(txtEditor.CaretIndex);
            var col = txtEditor.CaretIndex - txtEditor.GetCharacterIndexFromLineIndex(row);

            lblCursorPosition.Text = $"Line {row + 1}, Char {col + 1}";
        }
    }
}

It's a simple text editor with a status bar:

Here's the equivalent program with the code in C# instead of XAML:

MainWindow.xaml:

MainWindow.xaml.cs:

using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;

namespace WpfTutorialStatusBarGridCs
{
    /// 

    /// Interaction logic for MainWindow.xaml
    /// 
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            var dock_panel = new DockPanel();

            Content = dock_panel;


            var status_bar = new StatusBar();

            dock_panel.Children.Add(status_bar);

            DockPanel.SetDock(status_bar, Dock.Bottom);

            var items_panel_template = new ItemsPanelTemplate();

            {
                var grid_factory = new FrameworkElementFactory(typeof(Grid));

                {
                    {
                        var col = new FrameworkElementFactory(typeof(ColumnDefinition));

                        col.SetValue(ColumnDefinition.WidthProperty, new GridLength(100));

                        grid_factory.AppendChild(col);
                    }

                    {
                        var col = new FrameworkElementFactory(typeof(ColumnDefinition));

                        col.SetValue(ColumnDefinition.WidthProperty, new GridLength(1, GridUnitType.Auto));

                        grid_factory.AppendChild(col);
                    }

                    {
                        var col = new FrameworkElementFactory(typeof(ColumnDefinition));

                        col.SetValue(ColumnDefinition.WidthProperty, new GridLength(1, GridUnitType.Star));

                        grid_factory.AppendChild(col);
                    }

                    {
                        var col = new FrameworkElementFactory(typeof(ColumnDefinition));

                        col.SetValue(ColumnDefinition.WidthProperty, new GridLength(1, GridUnitType.Auto));

                        grid_factory.AppendChild(col);
                    }

                    {
                        var col = new FrameworkElementFactory(typeof(ColumnDefinition));

                        col.SetValue(ColumnDefinition.WidthProperty, new GridLength(100));

                        grid_factory.AppendChild(col);
                    }
                }

                items_panel_template.VisualTree = grid_factory;
            }

            status_bar.ItemsPanel = items_panel_template;



            var text_block = new TextBlock();


            {
                var status_bar_item = new StatusBarItem();

                Grid.SetColumn(status_bar_item, 0);

                status_bar_item.Content = text_block;

                status_bar.Items.Add(status_bar_item);
            }

            {
                var separator = new Separator();

                Grid.SetColumn(separator, 1);

                status_bar.Items.Add(separator);
            }

            {
                var status_bar_item = new StatusBarItem();

                Grid.SetColumn(status_bar_item, 2);

                status_bar_item.Content = new TextBlock() { Text = "abc" };

                status_bar.Items.Add(status_bar_item);
            }

            {
                var separator = new Separator();

                Grid.SetColumn(separator, 3);

                status_bar.Items.Add(separator);
            }

            {
                var status_bar_item = new StatusBarItem();

                Grid.SetColumn(status_bar_item, 4);

                status_bar_item.Content = new ProgressBar() { Value = 50, Width = 90, Height = 16 };

                status_bar.Items.Add(status_bar_item);
            }

            {
                var text_box = new TextBox() { AcceptsReturn = true };

                text_box.SelectionChanged += (sender, e) => 
                {
                    var row = text_box.GetLineIndexFromCharacterIndex(text_box.CaretIndex);
                    var col = text_box.CaretIndex - text_box.GetCharacterIndexFromLineIndex(row);

                    text_block.Text = $"Line {row + 1}, Char {col + 1}";
                };

                dock_panel.Children.Add(text_box);
            }
        }
    }
}

The C# version is much more verbose. However, with the help of some extension methods, it can be written in a fluent style, eliminating the intermediate variables:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        var text_block = new TextBlock();

        Content = new DockPanel()

            .AddChildren(

                new StatusBar()
                    .SetDock(Dock.Bottom)
                    .SetItemsPanel(
                        new ItemsPanelTemplate()
                            .SetVisualTree(
                                new FrameworkElementFactory(typeof(Grid))
                                    .AppendChildren(
                                        new FrameworkElementFactory(typeof(ColumnDefinition))
                                            .SetValue_(ColumnDefinition.WidthProperty, new GridLength(100)),
                                        new FrameworkElementFactory(typeof(ColumnDefinition))
                                            .SetValue_(ColumnDefinition.WidthProperty, new GridLength(1, GridUnitType.Auto)),
                                        new FrameworkElementFactory(typeof(ColumnDefinition))
                                            .SetValue_(ColumnDefinition.WidthProperty, new GridLength(1, GridUnitType.Star)),
                                        new FrameworkElementFactory(typeof(ColumnDefinition))
                                            .SetValue_(ColumnDefinition.WidthProperty, new GridLength(1, GridUnitType.Auto)),
                                        new FrameworkElementFactory(typeof(ColumnDefinition))
                                            .SetValue_(ColumnDefinition.WidthProperty, new GridLength(100)))))
                    .AddItems(
                        new StatusBarItem() { Content = text_block }.SetColumn(0),
                        new Separator().SetColumn(1),
                        new StatusBarItem() { Content = new TextBlock() { Text = "abc" } }.SetColumn(2),
                        new Separator().SetColumn(3),
                        new StatusBarItem() { Content = new ProgressBar() { Value = 50, Width = 90, Height = 16 } }.SetColumn(4)),

                new TextBox() { AcceptsReturn = true }
                    .AddSelectionChanged(
                        (sender, e) =>
                        {
                            var box = sender as TextBox;

                            var row = box.GetLineIndexFromCharacterIndex(box.CaretIndex);
                            var col = box.CaretIndex - box.GetCharacterIndexFromLineIndex(row);

                            text_block.Text = $"Line {row + 1}, Char {col + 1}";
                        }));
    }
}

Here are the extension methods used:

public static class Extensions
{
    public static T SetDock(this T element, Dock dock) where T : UIElement
    {
        DockPanel.SetDock(element, dock);

        return element;
    }

    public static T SetColumn(this T element, int value) where T : UIElement
    {
        Grid.SetColumn(element, value);

        return element;
    }

    public static T SetValue_(this T factory, DependencyProperty dp, object value) where T : FrameworkElementFactory
    {
        factory.SetValue(dp, value);

        return factory;
    }

    public static T AppendChildren(this T factory, params FrameworkElementFactory[] children) where T : FrameworkElementFactory
    {
        foreach (var child in children)
            factory.AppendChild(child);

        return factory;
    }

    public static T SetVisualTree(this T template, FrameworkElementFactory factory) where T : FrameworkTemplate
    {
        template.VisualTree = factory;

        return template;
    }

    public static T1 SetItemsPanel(this T1 control, T2 template) where T1 : ItemsControl where T2 : ItemsPanelTemplate
    {
        control.ItemsPanel = template;

        return control;
    }

    public static T AddItems(this T control, params object[] items) where T : ItemsControl
    {
        foreach (var item in items)
            control.Items.Add(item);

        return control;
    }

    public static T AddSelectionChanged(this T obj, RoutedEventHandler handler) where T : TextBoxBase
    {
        obj.SelectionChanged += handler;

        return obj;
    }

    public static T1 AddChildren(this T1 panel, params UIElement[] elements) where T1 : Panel
    {
        foreach (var elt in elements)
            panel.Children.Add(elt);

        return panel;
    }

}