type-safe collection

[Gary]

I would like to make a strongly typed, sortable collection by leveraging a
Framework class. I began by looking at CollectionBase but it doesn't have
built-int sorting. I would prefer to derive from ArrayList, but if I code
an Add(MyElement) method, the original Add(object) remains exposed,
compromising type safety. I know this must be a common task, how to do it?
Thanks,
Gary

[Gary]

Newbie: I would like to make a strongly typed, sortable collection by

leveraging a
Framework class. I began by looking at CollectionBase but it doesn't have

built-in sorting. I would prefer to derive from ArrayList, but if I code

[Jeff Louie]

Gary... You could write a base class that contains an array list by
ownership and then extend from this base class.

http://www.geocities.com/jeff_louie/OOP/oop7.htm

Regards,
Jeff

>I would prefer to derive from ArrayList, but if I code
an Add(MyElement) method, the original Add(object) remains exposed,
compromising type safety.<

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[no potted meat@hotmail.com David Browne]

"Gary" <gf...@thoughtvector.com> wrote in message
news:40035be6$0$62215$9a6e...@news.newshosting.com...

Override Add(Object) and check the type of the input object, and throw an
exception if it is the wrong type. Not a perfect solution, since it is a
run-time error, but strongly-typed collections won't be right until
generics, anyway.

David

[Daniel O'Connell]

CollectionBase uses an array list internally(the protected InnerList
property). You should be able to simply call down to the sort method on that
via your own using hte containment method Jeff Louie suggested.

"Gary" <gf...@thoughtvector.com> wrote in message

news:40035b72$0$62138$9a6e...@news.newshosting.com...

[Jay B. Harlow [MVP - Outlook]]

Gary,

> I would like to make a strongly typed, sortable collection by leveraging a
> Framework class. I began by looking at CollectionBase but it doesn't have
> built-int sorting.

CollectionBase has "built-in" sorting by virtue its a wrapper around an
ArrayList, the ArrayList itself is exposed via the protected
CollectionBase.InnerList property.

If your class needs to support Sort itself, I would recommend delegation to
the InnerList sort methods.

Something like (untested):

using System.Collections;

class MyCollection : CollectionBase
{

...

void Sort()
{
base.InnerList.Sort()
}
void Sort(IComparer comparer)
{
base.InnerList.Sort(comparer)
}
void Sort(int index, int count, IComparer comparer)
{
base.InnerList.Sort(index, count, comparer)
}
}

Hope this helps
Jay

"Gary" <gf...@thoughtvector.com> wrote in message
news:40035b72$0$62138$9a6e...@news.newshosting.com...

[Ignacio Machin \( .NET/ C# MVP \)]

Hi Gary,

Please find below an example of a strong typed collection, as you can see
the correct way of doing so is extending CollectionBase.
The only functionality not provided is Sort, for this I implemented a class
: ClassSorter , it use reflection to sort any class based on a property
without need anything from the sortee class.
If you have any doubt let me know.

Pd:
The code is not well commented as I got it from the current working project
that is not well documented yet.
The Collection is a collection of a class type named Location, you need to
change this to your correct type.
If you look the Sort method of the collection class you will see that the
first parameter is the name of the property that will be used as sort
criteria.

Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

public class LocationCollection:CollectionBase
{
public Location Insert( int index, Location newelem )
{
this.InnerList.Insert( index, newelem);
return newelem;
}
public Location Add( Location newelem)
{
this.InnerList.Add( newelem);
return newelem;
}

public Location this[int index]
{
get
{
return (Location) InnerList[index];
}
set
{
InnerList[index] = value;
}
}

public Location Find(int id)
{
foreach(Location current in InnerList)
if ( current.ID == id )
return current;
return null;
}

public void Remove( Location elem)
{
InnerList.Remove( elem);

}

public LocationCollection(){}
private LocationCollection( ArrayList newarray)
{
InnerList.Clear();
foreach( Location location in newarray)
{
Add( location);
}
}

public LocationCollection Sort( string sortParam,
fatalcrashCore.SortDirection direction)
{
ArrayList newlist = (ArrayList)InnerList.Clone();
ClassSorter sorter = new ClassSorter( sortParam, SortByType.Property,
direction);
newlist.Sort( sorter);
return new LocationCollection( newlist);
}

public LocationCollection Clone()
{
return new LocationCollection( InnerList);
}

public LocationCollection Search(FilterCollection filters, bool AND)
{
LocationCollection filtered = new LocationCollection ();
foreach(Location point in InnerList)
{
bool matched = false;
foreach(FilterBase filter in filters)
if ( filter.Match(point) )
{
matched = true;
if ( !AND )
break;
}
else
{
if ( AND )
{
matched = false;
break;
}
}
if ( matched )
filtered.Add( point);

}
return filtered;
}

}

public class ClassSorter: IComparer
{
protected string sortBy;
protected SortByType sortByType;
protected SortDirection sortDirection;

#region Constructors
public ClassSorter(string sortBy, SortByType sortByType, SortDirection
sortDirection)
{
this.sortBy = sortBy;
this.sortByType = sortByType;
this.sortDirection = sortDirection;
}
#endregion

int Compare( object x, object y, string comparer)
{
if ( comparer.IndexOf( ".") != -1 )
{
//split the string
string[] parts = comparer.Split( new char[]{ '.'} );
return Compare( x.GetType().GetProperty( parts[0]).GetValue(x, null) ,
y.GetType().GetProperty( parts[0]).GetValue(y, null) , parts[1]
);
}
else
{
IComparable icx, icy;
icx =
(IComparable)x.GetType().GetProperty( comparer).GetValue(x, null);
icy =
(IComparable)y.GetType().GetProperty( comparer).GetValue(y, null);

if ( x.GetType().GetProperty(comparer).PropertyType ==
typeof(System.String) )
{
icx = (IComparable) icx.ToString().ToUpper();
icy = (IComparable) icy.ToString().ToUpper();
}

if(this.sortDirection == SortDirection.Descending)
return icy.CompareTo(icx);
else
return icx.CompareTo(icy);
}

}

public int Compare(object x, object y)
{
return Compare( x, y, sortBy);
}

}

public enum SortByType
{
Method = 0,
Property = 1
}

public enum SortDirection
{
Ascending = 0,
Descending = 1
}

"Gary" <gf...@thoughtvector.com> wrote in message
news:40035b72$0$62138$9a6e...@news.newshosting.com...

[Gary]

Thanks for all the great suggestions, folks, stuff for me to chew on!
Gary

"Gary" <gf...@thoughtvector.com> wrote in message
news:40035b72$0$62138$9a6e...@news.newshosting.com...

[Gary]

Thanks, I wasn't aware of this. This looks like the least effort route to
the solution.
Gary

"Jay B. Harlow [MVP - Outlook]" <Jay_Har...@msn.com> wrote in message
news:etUIn1Y2...@TK2MSFTNGP09.phx.gbl...

[Jay B. Harlow [MVP - Outlook]]

Gary,
FYI: the DictionaryBase is a wrapper around Hashtable, the Hashtable itself
is exposed via the DictionaryBase.InnerHashtable.

I actually wrote my own DictionaryBase & CollectionBase, that allow the
developer to can change the wrapped collection. Which reminds me, I need to
post them someplace convenient for others ;-)

Hope this helps
Jay

"Gary" <gf...@thoughtvector.com> wrote in message

news:40042b5e$0$2652$9a6e...@news.newshosting.com...

[Jacob]

Strong-Typed collections based on CollectionBase, or an ArrayList???? Sure
you could wrap it up and make it a strong-typed collection, but everything
is still going to get cast as an object, and that will have a serious affect
on performance. The easiest way to learn strong type collections or have
one made for you is to use CollectionGen for CodeSmith:

http://www.sellsbrothers.com/tools/
http://www.kynosarges.de/Templates.html

I now write all my collections manually and I can always get better
performance out of them than the standard .NET collection.

Hope this helps,
Jacob

"Gary" <gf...@thoughtvector.com> wrote in message
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