using System;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Input;

using System.Windows.Media;

namespace LY.SetSpaceProperty

{

    public class SpaceButton : Button

    {

        //传统的字段和属性

        string txt;

        public string Text

        {

            set

            {

                txt = value;

                Content = SpaceOutText(txt);

            }

            get

            {

                return txt;

            }

        }

        //依赖属性

        public static readonly DependencyProperty SpaceProperty;

        public int Space

        {

            set

            {

                SetValue(SpaceProperty, value);

            }

            get

            {

                return (int)GetValue(SpaceProperty);

            }

        }

        //用静态构造函数初始化

        static SpaceButton()

        {

            //定义元数据

            FrameworkPropertyMetadata metadata = new FrameworkPropertyMetadata();

            metadata.DefaultValue = 1;

            metadata.AffectsMeasure = true;

            metadata.Inherits = true;

            metadata.PropertyChangedCallback += OnSpacePropertyChanged;

            // 注册到依赖属性

            SpaceProperty =

                DependencyProperty.Register("Space", typeof(int),

                                            typeof(SpaceButton), metadata,

                                            ValidateSpaceValue);

        }

        //回调方法用于值的验证

        static bool ValidateSpaceValue(object obj)

        {

            int i = (int)obj;

            return i >= 0;

        }

        //回调方法用于属性改变

        static void OnSpacePropertyChanged(DependencyObject obj,

                                    DependencyPropertyChangedEventArgs args)

        {

            SpaceButton btn = obj as SpaceButton;

            btn.Content = btn.SpaceOutText(btn.txt);

        }

        string SpaceOutText(string str)

        {

            if (str == null)

                return null;

            StringBuilder build = new StringBuilder();

            foreach (char ch in str)

                build.Append(ch + new string(' ', Space));

            return build.ToString();

        }

    }

}