WPF Control Factory

using System;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;
using Pfz.DataTypes;
using Pfz.Ranges;

namespace Pfz.WpfControls
{
	/// <summary>
	/// Control used to edit ranges. It displays a slider and a text-box for editing
	/// values.
	/// </summary>
	/// <typeparam name="TRange">The type of the range used.</typeparam>
	public class RangeControl<TRange>:
		Grid,
		IValueControl,
		IValueContainer<TRange>
	where
		TRange: IRange
	{
		private Slider fSlider = new Slider();
		private TextBox fTextBox = new TextBox();
		internal ColumnDefinition fTextBoxColumn;
		
		private static readonly Type fPropertyDataType;
		private static readonly ConstructorInfo fRangeConstructor;
		
		/// <summary>
		/// Gets some information for the Range type only once.
		/// </summary>
		static RangeControl()
		{
			var propertyType = typeof(TRange);
			while(propertyType != null)
			{
				if (propertyType.IsGenericType)
				{
					if (propertyType.GetGenericTypeDefinition() == typeof(Range<>))
					{
						Type dataType = propertyType.GetGenericArguments()[0];
						fPropertyDataType = dataType;
						fRangeConstructor = typeof(TRange).GetConstructor(new Type[]{dataType});
						return;
					}
				}
				
				propertyType = propertyType.BaseType;
			}
			
			throw new ApplicationException("Can't find the Range constructor.");
		}
		
		/// <summary>
		/// Creates a new RangeControl.
		/// </summary>
		public RangeControl()
		{
			ColumnDefinition columnSlider = new ColumnDefinition();
			columnSlider.Width = new GridLength(1, GridUnitType.Star);
			ColumnDefinitions.Add(columnSlider);

			ColumnDefinition columnTextBox = new ColumnDefinition();
			columnTextBox.Width = new GridLength(100, GridUnitType.Pixel);
			ColumnDefinitions.Add(columnTextBox);
			fTextBoxColumn = columnTextBox;

			RowDefinition row = new RowDefinition();
			row.Height = new GridLength(1, GridUnitType.Star);
			RowDefinitions.Add(row);
			
			Children.Add(fSlider);
			Children.Add(fTextBox);

			Grid.SetColumn(fSlider, 0);
			Grid.SetRow(fSlider, 0);
			Grid.SetColumn(fTextBox, 1);
			Grid.SetRow(fTextBox, 0);

			fSlider.ValueChanged += fSlider_ValueChanged;
			fTextBox.LostFocus += fTextBox_LostFocus;

			var attribute = Range.GetRangeAttribute(typeof(TRange));
			fSlider.Minimum = Convert.ToDouble(attribute.MinimumValue);
			fSlider.Maximum = Convert.ToDouble(attribute.MaximumValue);
			p_GetSliderValue();
		}
		
		void fTextBox_LostFocus(object sender, RoutedEventArgs e)
		{
			try
			{
				double result;
				if (double.TryParse(fTextBox.Text, out result))
					fSlider.Value = result;
				else
					p_GetSliderValue();
			}
			catch
			{
				p_GetSliderValue();
			}
		}

		void fSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
		{
			p_GetSliderValue();
		}
		private void p_GetSliderValue()
		{
			var dataType = fPropertyDataType;
			if (dataType == null)
			{
				fTextBox.Text = fSlider.Value.ToString();
				return;
			}
			
			object value = Convert.ChangeType(fSlider.Value, dataType);
			fTextBox.Text = value.ToString();
		}
		
		/// <summary>
		/// Clears the value of this control.
		/// </summary>
		public void Clear()
		{
			fSlider.Value = fSlider.Minimum;
		}
		
		/// <summary>
		/// Gets or sets a value indicating that this control should be read-only.
		/// </summary>
		public bool IsReadOnly
		{
			get
			{
				return !IsEnabled;
			}
			set
			{
				IsEnabled = !value;
			}
		}
		
		/// <summary>
		/// Gets or sets the range value.
		/// </summary>
		public TRange Value
		{
			get
			{
				var value = fSlider.Value;
				var typedValue = Convert.ChangeType(value, fPropertyDataType);
				var range = fRangeConstructor.Invoke(new object[]{typedValue});
				return (TRange)range;
			}
			set
			{
				if (value == null)
					fSlider.Value = 0;
				else
					fSlider.Value = Convert.ToDouble(value.Value);
			}
		}
		
		#region IValueContainer Members
			object IValueContainer.Value
			{
				get
				{
					return Value;
				}
				set
				{
					Value = (TRange)value;
				}
			}
		#endregion
	}
}