Let TextBox stretch to fill width in StackPanel

Question

I have a StackPanel in my WinRT C# Metro app that I want to use as container for a label/value pair (TextBlock and TextBox) like this:

Answer 1

Came across this question while looking up whether a WinRT DockPanel existed.

I ended up slightly modifying the DockPanel that comes with the Silverlight Toolkit, and it seems to work.

To use, add xmlns:toolkit="using:System.Windows.Controls" to the top, and taking the question above as the scenario, we could write:

DockPanel.cs:

// (c) Copyright Microsoft Corporation.
// This source is subject to the Microsoft Public License (Ms-PL).
// Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
// All other rights reserved.

// Modified slightly for Windows Runtime support.

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

namespace System.Windows.Controls
{
    public enum Dock
    {
        // Summary:
        //     Specifies that the control should be positioned on the left of the control.
        Left = 0,
        //
        // Summary:
        //     Specifies that the control should be positioned on top of the control.
        Top = 1,
        //
        // Summary:
        //     Specifies that the control should be positioned on the right of the control.
        Right = 2,
        //
        // Summary:
        //     Specifies that the control should be positioned at the bottom of the control.
        Bottom = 3,
    }

    /// 

    /// Arranges child elements around the edges of the panel.  Optionally, 
    /// last added child element can occupy the remaining space.
    /// 
    /// Stable
    public class DockPanel : Panel
    {
        /// 

        /// A value indicating whether a dependency property change handler
        /// should ignore the next change notification.  This is used to reset
        /// the value of properties without performing any of the actions in
        /// their change handlers.
        /// 
        private static bool _ignorePropertyChange;

        #region public bool LastChildFill
        /// 

        /// Gets or sets a value indicating whether the last child element
        /// added to a 
        /// resizes to fill the remaining space.
        /// 
        /// 
        /// True if the last element added resizes to fill the remaining space,
        /// false to indicate the last element does not resize. The default is
        /// true.
        /// 
        public bool LastChildFill
        {
            get { return (bool)GetValue(LastChildFillProperty); }
            set { SetValue(LastChildFillProperty, value); }
        }

        /// 

        /// Identifies the
        /// 
        /// dependency property.
        /// 
        public static readonly DependencyProperty LastChildFillProperty =
            DependencyProperty.Register(
                "LastChildFill",
                typeof(bool),
                typeof(DockPanel),
                new PropertyMetadata(true, OnLastChildFillPropertyChanged));

        /// 

        /// LastChildFillProperty property changed handler.
        /// 
        /// DockPanel that changed its LastChildFill.
        /// Event arguments.
        private static void OnLastChildFillPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            DockPanel source = d as DockPanel;
            source.InvalidateArrange();
        }
        #endregion public bool LastChildFill

        #region public attached Dock Dock
        /// 

        /// Gets the value of the
        ///  attached
        /// property for the specified element.
        /// 
        /// 
        /// The element from which the property value is read.
        /// 
        /// 
        /// The  property
        /// value for the element.
        /// 
        [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "DockPanel only has UIElement children")]
        public static Dock GetDock(UIElement element)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            return (Dock)element.GetValue(DockProperty);
        }

        /// 

        /// Sets the value of the
        ///  attached
        /// property for the specified element to the specified dock value.
        /// 
        /// 
        /// The element to which the attached property is assigned.
        /// 
        /// 
        /// The dock value to assign to the specified element.
        /// 
        [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "DockPanel only has UIElement children")]
        public static void SetDock(UIElement element, Dock dock)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            element.SetValue(DockProperty, dock);
        }

        /// 

        /// Identifies the
        /// 
        /// attached property.
        /// 
        public static readonly DependencyProperty DockProperty =
            DependencyProperty.RegisterAttached(
                "Dock",
                typeof(Dock),
                typeof(DockPanel),
                new PropertyMetadata(Dock.Left, OnDockPropertyChanged));

        /// 

        /// DockProperty property changed handler.
        /// 
        /// UIElement that changed its Dock.
        /// Event arguments.
        [SuppressMessage("Microsoft.Usage", "CA2208:InstantiateArgumentExceptionsCorrectly", Justification = "Almost always set from the attached property CLR setter.")]
        private static void OnDockPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            // Ignore the change if requested
            if (_ignorePropertyChange)
            {
                _ignorePropertyChange = false;
                return;
            }

            UIElement element = (UIElement)d;
            Dock value = (Dock)e.NewValue;

            // Validate the Dock property
            if ((value != Dock.Left) &&
                (value != Dock.Top) &&
                (value != Dock.Right) &&
                (value != Dock.Bottom))
            {
                // Reset the property to its original state before throwing
                _ignorePropertyChange = true;
                element.SetValue(DockProperty, (Dock)e.OldValue);

                string message = string.Format(
                    CultureInfo.InvariantCulture,
                    "InvalidValue",
                    value);
                throw new ArgumentException(message, "value");
            }

            // Cause the DockPanel to update its layout when a child changes
            DockPanel panel = VisualTreeHelper.GetParent(element) as DockPanel;
            if (panel != null)
            {
                panel.InvalidateMeasure();
            }
        }
        #endregion public attached Dock Dock

        /// 

        /// Initializes a new instance of the
        ///  class.
        /// 
        public DockPanel()
        {
        }

        /// 

        /// Measures the child elements of a
        ///  in preparation
        /// for arranging them during the
        /// 
        /// pass.
        /// 
        /// 
        /// The area available to the
        /// .
        /// 
        /// 
        /// The desired size of the
        /// .
        /// 
        [SuppressMessage("Microsoft.Naming", "CA1725:ParameterNamesShouldMatchBaseDeclaration", MessageId = "0#", Justification = "Compat with WPF.")]
        protected override Size MeasureOverride(Size constraint)
        {
            double usedWidth = 0.0;
            double usedHeight = 0.0;
            double maximumWidth = 0.0;
            double maximumHeight = 0.0;

            // Measure each of the Children
            foreach (UIElement element in Children)
            {
                // Get the child's desired size
                Size remainingSize = new Size(
                    Math.Max(0.0, constraint.Width - usedWidth),
                    Math.Max(0.0, constraint.Height - usedHeight));
                element.Measure(remainingSize);
                Size desiredSize = element.DesiredSize;

                // Decrease the remaining space for the rest of the children
                switch (GetDock(element))
                {
                    case Dock.Left:
                    case Dock.Right:
                        maximumHeight = Math.Max(maximumHeight, usedHeight + desiredSize.Height);
                        usedWidth += desiredSize.Width;
                        break;
                    case Dock.Top:
                    case Dock.Bottom:
                        maximumWidth = Math.Max(maximumWidth, usedWidth + desiredSize.Width);
                        usedHeight += desiredSize.Height;
                        break;
                }
            }

            maximumWidth = Math.Max(maximumWidth, usedWidth);
            maximumHeight = Math.Max(maximumHeight, usedHeight);
            return new Size(maximumWidth, maximumHeight);
        }

        /// 

        /// Arranges the child elements of the
        ///  control.
        /// 
        /// 
        /// The area in the parent element that the
        ///  should use to
        /// arrange its child elements.
        /// 
        /// 
        /// The actual size of the
        ///  after the child
        /// elements are arranged. The actual size should always equal
        /// .
        /// 
        [SuppressMessage("Microsoft.Naming", "CA1725:ParameterNamesShouldMatchBaseDeclaration", MessageId = "0#", Justification = "Compat with WPF.")]
        protected override Size ArrangeOverride(Size arrangeSize)
        {
            double left = 0.0;
            double top = 0.0;
            double right = 0.0;
            double bottom = 0.0;

            // Arrange each of the Children
            UIElementCollection children = Children;
            int dockedCount = children.Count - (LastChildFill ? 1 : 0);
            int index = 0;
            foreach (UIElement element in children)
            {
                // Determine the remaining space left to arrange the element
                Rect remainingRect = new Rect(
                    left,
                    top,
                    Math.Max(0.0, arrangeSize.Width - left - right),
                    Math.Max(0.0, arrangeSize.Height - top - bottom));

                // Trim the remaining Rect to the docked size of the element
                // (unless the element should fill the remaining space because
                // of LastChildFill)
                if (index < dockedCount)
                {
                    Size desiredSize = element.DesiredSize;
                    switch (GetDock(element))
                    {
                        case Dock.Left:
                            left += desiredSize.Width;
                            remainingRect.Width = desiredSize.Width;
                            break;
                        case Dock.Top:
                            top += desiredSize.Height;
                            remainingRect.Height = desiredSize.Height;
                            break;
                        case Dock.Right:
                            right += desiredSize.Width;
                            remainingRect.X = Math.Max(0.0, arrangeSize.Width - right);
                            remainingRect.Width = desiredSize.Width;
                            break;
                        case Dock.Bottom:
                            bottom += desiredSize.Height;
                            remainingRect.Y = Math.Max(0.0, arrangeSize.Height - bottom);
                            remainingRect.Height = desiredSize.Height;
                            break;
                    }
                }

                element.Arrange(remainingRect);
                index++;
            }

            return arrangeSize;
        }
    }
}