Property grid ExpandableObjec tConverter DoubleClick problem.

[Vladimir.Sakharuk]

I have created ExpandableObjec tConverter in C#. for use in
System.Windows. Forms.PropertyG rid.
The property grid shows the DiffItem is a object that holds member
TheItem.

without expanding TheItem
It works if u click, select from drop down box. until you DoubleClick
it shows error:
"Invalid property Value". with "Object type cannot be converted to
target type."

Here is a code:

public class ItemConverter:E xpandableObject Converter
{
public override bool CanConvertTo(IT ypeDescriptorCo ntext context, Type
destinationType )
{
if(destinationT ype == typeof(TheItem) ) return true;
return base.CanConvert To (context, destinationType );
}
public override object ConvertTo(IType DescriptorConte xt context,
CultureInfo culture, object value, Type destinationType )
{
if(destinationT ype == typeof(System.S tring) && value is TheItem)
{
return ((TheItem)value ).Rating;
}
object ret = base.ConvertTo (context, culture, value, destinationType );
//Line 1
return ret;
}
public override bool GetStandardValu esSupported( ITypeDescriptor Context
context)
{
return true;
}
public override bool GetStandardValu esExclusive( ITypeDescriptor Context
context)
{
return true;
}
public override StandardValuesC ollection
GetStandardValu es(ITypeDescrip torContext context)
{
if( context.Instanc e is DiffItem )
{
//Line 2
return new StandardValuesC ollection(new string[]
{"N/R","A","B","C", "D","E"});
}
return base.GetStandar dValues (context);
}

public override bool CanConvertFrom( ITypeDescriptor Context context,
Type sourceType)
{
if(sourceType == typeof(string))
return true;
return base.CanConvert From (context, sourceType);
}
public override object ConvertFrom(ITy peDescriptorCon text context,
CultureInfo culture, object value)
{
if( value is string )
{
if(context.Inst ance is TheItem)
{
TheItem item = new TheItem((string ) value,DateTime. Now);
return item;
}
if( context.Instanc e is DiffItem )
{
DiffItem diff = (DiffItem )context.Instan ce;
TheItem rating=diff.Rat ing;
TheItem item = new TheItem ((string) value,rating.th eDate);
return item;
}
}
return base.ConvertFro m (context, culture, value);
}
}

//the Item class
[TypeConverterAt tribute(typeof( ItemConverter))]
public class TheItem
{
string rating="N/A";
DateTime theDate=DateTim e.Min;
#region Constructors
public TheItem()
{}

public TheItem(string value, DateTime thedate )
{
this.rating=val ue;
this.theDate=th edate ;
}
#endregion

#region Properties

[DescriptionAttr ibute("The Rating itself."),
DefaultValueAtt ribute("N/A"),
RefreshProperti esAttribute(Ref reshProperties. All),
ReadOnlyAttribu te(false)]
public string Rating
{
get{return rating;}
set{rating=valu e;}
}
[DescriptionAttr ibute("Rating Date."),
ReadOnlyAttribu te(false)]
public DateTime RatingDate
{
get{return theDate;}
set{theDate=val ue;}
}
#endregion
}
}

where DiffItem is a object that holds member TheItem:
[CategoryAttribu te("Ratings"),
ReadOnlyAttribu te(false)]
public TheItem TheRating
{
get { return rating; }
set { rating=value; }
}

I have debug the code...
it goes to //line 2 (see the code)
and gets the values.
then it goes to //line 1
and loop trough all possible values.
The again goes to //line 2 and then shows the error.
Any help how to fix this welcome.
Thank you \/|@d.