Question about Property Dependency example

Question

In Visual C # 2010 Recipes: An Approach to Problem Solving , there is an example that demonstrates the power of dependency properties. This example describes a UserControl that has two properties, TextFontWeight and TextContent, that have the dependency properties TextFontWeightProperty and TextContentProperty, respectively.

XAML code is as follows

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace TestWpfApplication
{
    /// <summary>
    /// Interaction logic for TestDpControl.xaml
    /// </summary>
    public partial class TestDpControl : UserControl
    {
        public TestDpControl()
        {
            InitializeComponent();
            DataContext = this;
        }

        public FontWeight TextFontWeight
        {
            get { return (FontWeight)GetValue(TextFontWeightProperty); }
            set { SetValue(TextFontWeightProperty, value); }

        }

        public string TextContent
        {
            get { return (string)GetValue(TextContentProperty); }
            set { SetValue(TextContentProperty, value); }


        }

        public static readonly DependencyProperty TextContentProperty =
            DependencyProperty.Register(
            "TextContent",
            typeof(string),
            typeof(TestDpControl),

            new FrameworkPropertyMetadata(
                "Default Value",
                FrameworkPropertyMetadataOptions.AffectsArrange
                & FrameworkPropertyMetadataOptions.AffectsMeasure
                & FrameworkPropertyMetadataOptions.AffectsRender));


        public static readonly DependencyProperty TextFontWeightProperty =
            DependencyProperty.Register(
            "TextFontWeight",
            typeof(FontWeight),
            typeof(TestDpControl),
            new FrameworkPropertyMetadata(FontWeights.Normal,
                FrameworkPropertyMetadataOptions.AffectsArrange
                & FrameworkPropertyMetadataOptions.AffectsMeasure
                & FrameworkPropertyMetadataOptions.AffectsRender,
                TextFontWeight_PropertyChanged,
                TextFontWeight_CoerceValue));

        private static object TextFontWeight_CoerceValue(DependencyObject d, object value)
        {
            FontWeight fontWeight = (FontWeight)value;
            if (fontWeight == FontWeights.Bold || fontWeight == FontWeights.Normal)
            {
                return fontWeight;
            }
            return FontWeights.Normal;

        }

        private static void TextFontWeight_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            TestDpControl myControl = d as TestDpControl;

            if (myControl != null)
            {
                FontWeight fontWeight = (FontWeight)e.NewValue;
                string fontWeightName;

                if (fontWeight == FontWeights.Bold)
                    fontWeightName = "Bold";
                else
                    fontWeightName = "Normal";
                myControl.txblFontWeight.Text = string.Format("Font weight set to:{0}.", fontWeightName);

            }


        }
    }}

, . getter, FontWeights.Bold TextFontWeight "Default Value" TextContent? , - Dependency .

Answer 1

, (), , - . , - , :

• Binding: , .
• : parent/ancestor.
• : , .

, , . , , . CLR ; getter setter GetValue SetValue, CLR .

Answer 2

DependencyProperties , XAML ( WPF IMHO).

:

http://joshsmithonwpf.wordpress.com/2007/05/16/demystifying-dependency-properties/

, XAML, INotifyPropertyChanged, .

Answer 3

, , /, , , . , DependencyProperties:

• WPF DataBinding (, , MVVM)
• XAML
• you can inherit DependencyProperties as so-called Attached Properties through controls without knowing each other
• ...

The list is much longer. If you intend to use user controls / user controls in WPF, you will see pretty quickly that DependencyProperties are very useful and necessary for developing a graphical interface, and not just for recommending Mircosoft.

Hope this was a little helpful.

Jan