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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.Design.Serialization;
using System.Globalization;
using System.Linq;
using System.Reflection;

/*
  Custom Type Converter Sample 3
  http://cyotek.com/blog/using-alternate-descriptions-for-enumeration-members
*/

namespace CustomTypeConverter3
{
  /// <summary>
  /// Converts lengths from one data type to another. Access this class through the <see cref="TypeDescriptor"/>.
  /// </summary>
  internal class LengthConverter : TypeConverter
  {
    #region Overridden Members

    /// <summary>
    /// Returns whether this converter can convert an object of the given type to the type of this converter, using the specified context.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    /// <param name="sourceType">A <see cref="T:System.Type" /> that represents the type you want to convert from.</param>
    /// <returns>true if this converter can perform the conversion; otherwise, false.</returns>
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
      return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);
    }

    ///// <summary>
    ///// Returns whether this converter can convert the object to the specified type, using the specified context.
    ///// </summary>
    ///// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    ///// <param name="destinationType">A <see cref="T:System.Type" /> that represents the type you want to convert to.</param>
    ///// <returns>true if this converter can perform the conversion; otherwise, false.</returns>
    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
    {
      return destinationType == typeof(InstanceDescriptor) || base.CanConvertTo(context, destinationType);
    }

    /// <summary>
    /// Converts the given object to the type of this converter, using the specified context and culture information.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    /// <param name="culture">The <see cref="T:System.Globalization.CultureInfo" /> to use as the current culture.</param>
    /// <param name="value">The <see cref="T:System.Object" /> to convert.</param>
    /// <returns>An <see cref="T:System.Object" /> that represents the converted value.</returns>
    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
      string stringValue;
      object result;

      result = null;
      stringValue = value as string;

      if (!string.IsNullOrEmpty(stringValue))
      {
        int nonDigitIndex;

        nonDigitIndex = stringValue.IndexOf(stringValue.FirstOrDefault(char.IsLetter));

        if (nonDigitIndex > 0)
        {
          result = new Length
          {
            Value = Convert.ToSingle(stringValue.Substring(0, nonDigitIndex)),
            Unit = EnumExtensions.GetValue(stringValue.Substring(nonDigitIndex), Unit.None)
          };
        }
      }

      return result ?? base.ConvertFrom(context, culture, value);
    }

    /// <summary>
    /// Converts the given value object to the specified type, using the specified context and culture information.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    /// <param name="culture">A <see cref="T:System.Globalization.CultureInfo" />. If null is passed, the current culture is assumed.</param>
    /// <param name="value">The <see cref="T:System.Object" /> to convert.</param>
    /// <param name="destinationType">The <see cref="T:System.Type" /> to convert the <paramref name="value" /> parameter to.</param>
    /// <returns>An <see cref="T:System.Object" /> that represents the converted value.</returns>
    /// <exception cref="System.ArgumentNullException">destinationType</exception>
    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
      Length length;
      object result;

      result = null;
      length = value as Length;

      if (length != null)
      {
        if (destinationType == typeof(string))
          result = length.ToString();
        else if (destinationType == typeof(InstanceDescriptor))
        {
          ConstructorInfo constructorInfo;

          constructorInfo = typeof(Length).GetConstructor(new[]
          {
            typeof(float), typeof(Unit)
          });
          result = new InstanceDescriptor(constructorInfo, new object[]
          {
            length.Value, length.Unit
          });
        }
      }

      return result ?? base.ConvertTo(context, culture, value, destinationType);
    }

    /// <summary>
    /// Returns a collection of properties for the type of array specified by the value parameter, using the specified context and attributes.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    /// <param name="value">An <see cref="T:System.Object" /> that specifies the type of array for which to get properties.</param>
    /// <param name="attributes">An array of type <see cref="T:System.Attribute" /> that is used as a filter.</param>
    /// <returns>A <see cref="T:System.ComponentModel.PropertyDescriptorCollection" /> with the properties that are exposed for this data type, or null if there are no properties.</returns>
    public override PropertyDescriptorCollection GetProperties(ITypeDescriptorContext context, object value, Attribute[] attributes)
    {
      return TypeDescriptor.GetProperties(value, attributes);
    }

    /// <summary>
    /// Returns whether this object supports properties, using the specified context.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    /// <returns>true if <see cref="M:System.ComponentModel.TypeConverter.GetProperties(System.Object)" /> should be called to find the properties of this object; otherwise, false.</returns>
    public override bool GetPropertiesSupported(ITypeDescriptorContext context)
    {
      return true;
    }

    /// <summary>
    /// Returns a collection of standard values for the data type this type converter is designed for when provided with a format context.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context that can be used to extract additional information about the environment from which this converter is invoked. This parameter or properties of this parameter can be null.</param>
    /// <returns>A <see cref="T:System.ComponentModel.TypeConverter.StandardValuesCollection" /> that holds a standard set of valid values, or null if the data type does not support a standard set of values.</returns>
    public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context)
    {
      List<Length> values;

      values = new List<Length>();
      values.Add(new Length(16, Unit.Pixel));
      values.Add(new Length(32, Unit.Pixel));
      values.Add(new Length(64, Unit.Pixel));
      values.Add(new Length(128, Unit.Pixel));

      return new StandardValuesCollection(values);
    }

    /// <summary>
    /// Returns whether this object supports a standard set of values that can be picked from a list, using the specified context.
    /// </summary>
    /// <param name="context">An <see cref="T:System.ComponentModel.ITypeDescriptorContext" /> that provides a format context.</param>
    /// <returns>true if <see cref="M:System.ComponentModel.TypeConverter.GetStandardValues" /> should be called to find a common set of values the object supports; otherwise, false.</returns>
    public override bool GetStandardValuesSupported(ITypeDescriptorContext context)
    {
      return true;
    }

    #endregion
  }
}