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//
// NullableConverter.cs
//
// Author:
// Atsushi Enomoto <atsushi@ximian.com>
// Ivan N. Zlatev <contact@i-nz.net>
//
// Copyright (C) 2007 Novell, Inc. http://www.novell.com
//
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
#if NET_2_0
using System;
using System.Collections;
using System.Globalization;
namespace System.ComponentModel
{
public class NullableConverter : TypeConverter
{
private Type nullableType;
private Type underlyingType;
private TypeConverter underlyingTypeConverter;
public NullableConverter (Type nullableType)
{
if (nullableType == null)
throw new ArgumentNullException ("nullableType");
this.nullableType = nullableType;
underlyingType = Nullable.GetUnderlyingType (nullableType);
underlyingTypeConverter = TypeDescriptor.GetConverter (underlyingType);
}
public override bool CanConvertFrom (ITypeDescriptorContext context, Type sourceType)
{
if (sourceType == underlyingType)
return true;
if (underlyingTypeConverter != null)
return underlyingTypeConverter.CanConvertFrom (context, sourceType);
return base.CanConvertFrom (context, sourceType);
}
public override bool CanConvertTo (ITypeDescriptorContext context, Type destinationType)
{
if (destinationType == underlyingType)
return true;
if (underlyingTypeConverter != null)
return underlyingTypeConverter.CanConvertTo (context, destinationType);
return base.CanConvertFrom (context, destinationType);
}
public override object ConvertFrom (ITypeDescriptorContext context, CultureInfo culture, object value)
{
// Because:
// 1) Nullable<> has an expliciit generic cast operator
// 2) We are returning an "Object" type here
// we don't have to bother creating the nullable instance,
// since the user will have to explicitly cast anyway.
//
if (value == null || value.GetType() == underlyingType)
return value;
if (value is string && String.IsNullOrEmpty ((string)value))
return null;
if (underlyingTypeConverter != null)
return underlyingTypeConverter.ConvertFrom (context, culture, value);
return base.ConvertFrom (context, culture, value);
}
public override object ConvertTo (ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
if (destinationType == null)
throw new ArgumentNullException ("destinationType");
// Explicit cast operator in Nullable when the user casts will take care
// of extracting the inner value.
if (destinationType == underlyingType && value.GetType() == nullableType)
return value;
if (underlyingTypeConverter != null && value != null)
return underlyingTypeConverter.ConvertTo (context, culture, value, destinationType);
return base.ConvertTo (context, culture, value, destinationType);
}
public override object CreateInstance (ITypeDescriptorContext context, IDictionary propertyValues)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.CreateInstance (context, propertyValues);
return base.CreateInstance (context, propertyValues);
}
public override bool GetCreateInstanceSupported (ITypeDescriptorContext context)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.GetCreateInstanceSupported (context);
return base.GetCreateInstanceSupported (context);
}
public override PropertyDescriptorCollection GetProperties (ITypeDescriptorContext context, object value, Attribute [] attributes)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.GetProperties (context, value, attributes);
return base.GetProperties (context, value, attributes);
}
public override bool GetPropertiesSupported (ITypeDescriptorContext context)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.GetCreateInstanceSupported (context);
return base.GetCreateInstanceSupported (context);
}
public override TypeConverter.StandardValuesCollection GetStandardValues (ITypeDescriptorContext context)
{
// Adds a "null" values to the standard values if supported and available
//
if (underlyingTypeConverter != null &&
underlyingTypeConverter.GetStandardValuesSupported (context)) {
TypeConverter.StandardValuesCollection values = underlyingTypeConverter.GetStandardValues (context);
if (values != null) {
ArrayList valuesWithNull = new ArrayList (values);
valuesWithNull.Add (null);
return new TypeConverter.StandardValuesCollection (valuesWithNull);
}
}
return base.GetStandardValues (context);
}
public override bool GetStandardValuesExclusive (ITypeDescriptorContext context)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.GetStandardValuesExclusive (context);
return base.GetStandardValuesExclusive (context);
}
public override bool GetStandardValuesSupported (ITypeDescriptorContext context)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.GetStandardValuesSupported (context);
return base.GetStandardValuesSupported (context);
}
public override bool IsValid (ITypeDescriptorContext context, object value)
{
if (underlyingTypeConverter != null)
return underlyingTypeConverter.IsValid (context, value);
return base.IsValid (context, value);
}
public Type NullableType {
get { return nullableType; }
}
public Type UnderlyingType {
get { return underlyingType; }
}
public TypeConverter UnderlyingTypeConverter {
get { return underlyingTypeConverter; }
}
}
}
#endif
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