Collections in C#

[Ricardo]

I'm trying to create a mechanism of sales. I have a Sales class and an Item
class. The Sales contains a lot of items. So, how can I make it?
If I use an array (public Item[] item) in the Sales class, I have to give
an inicial size for the array and this is bad (I don't know how many items
I will have).

[Jay Glynn]

You can either look at using ArrayList, it's dynamic and can grow as needed
or you can create your own collection class. If that is what you wish look
at using CollectionBase as your base class.

"Ricardo" <rmendes@aksistemas.com.br> wrote in message
news:3d469a9e$1@10.1.10.29...
>
> I'm trying to create a mechanism of sales. I have a Sales class and an
Item
> class. The Sales contains a lot of items. So, how can I make it?
> If I use an array (public Item[] item) in the Sales class, I have to give
> an inicial size for the array and this is bad (I don't know how many items
> I will have).
>

[Simon Franklin]

"Jay Glynn" <jlsglynn@hotmail.com> wrote:
>You can either look at using ArrayList, it's dynamic and can grow as needed
>or you can create your own collection class. If that is what you wish look
>at using CollectionBase as your base class.
>
>"Ricardo" <rmendes@aksistemas.com.br> wrote in message
>news:3d469a9e$1@10.1.10.29...
>>
>> I'm trying to create a mechanism of sales. I have a Sales class and an
>Item
>> class. The Sales contains a lot of items. So, how can I make it?
>> If I use an array (public Item[] item) in the Sales class, I have to give
>> an inicial size for the array and this is bad (I don't know how many items
>> I will have).
>>
>
>
The following two classes show how to create a collection class that holds
a list of Authors modify the code to your own design and enjoy.

/// <summary>
/// Summary description for the Author class.
/// </summary>
[Serializable]
public class Author
{
/// <summary>
/// Summary description for private String authorid;.
/// </summary>
private String authorid;
/// <summary>
/// Summary description for private String firstname;.
/// </summary>
private String firstname;
/// <summary>
/// Summary description for private String lastname;.
/// </summary>
private String lastname;
/// <summary>
/// Summary description for Property AuthorID .
/// </summary>
public String AuthorID
{
get
{
return authorid;
}
set
{
authorid = value;
}
}
/// <summary>
/// Summary description for Property FirstName .
/// </summary>
public String FirstName
{
get
{
return firstname;
}
set
{
firstname = value;
}
}
/// <summary>
/// Summary description for Property LastName .
/// </summary>
public String LastName
{
get
{
return lastname;
}
set
{
lastname = value;
}
}
/// <summary>
/// Summary description for Author().
/// </summary>
public Author()
{

}
/// <summary>
/// Summary description for Author(String authorid,String firstname,String
lastname,AuthorAddress address).
/// </summary>
public Author(String authorid,String firstname,String lastname)
{
this.AuthorID = authorid;
this.FirstName = firstname;
this.LastName = lastname;
}
/// <summary>
/// Summary description for Author(Author AuthorDetails).
/// </summary>
public Author(Author AuthorDetails)
{
this.AuthorID = AuthorDetails.AuthorID;
this.FirstName = AuthorDetails.FirstName;
this.LastName = AuthorDetails.LastName;
}
}
/// <summary>
/// Summary description for public class AuthorsCollection : System.Collections.CollectionBase
/// </summary>
[Serializable]
public class AuthorsCollection : System.Collections.CollectionBase
{
/// <summary>
/// Summary description for public Author this[int index].
/// </summary>
public Author this[int index]

{
get
{
return (Author) List[index];
}
set
{
List[index] = value;
}
}
/// <summary>
/// Summary description for public Author item(int index).
/// </summary>
public Author item(int index)

{
return (Author) List[index];
}

/// <summary>
/// Summary description for public void Add(AssociateContentItem ContentItem).
/// </summary>
public void Add(Author AuthorItem)
{
List.Add(AuthorItem);
}

/// <summary>
/// Summary description for public void Remove(int index).
/// </summary>
public void Remove(int index)
{
if (index > Count - 1 || index < 0)
{
///
}
else
{
List.RemoveAt(index);
}
}
/// <summary>
/// Summary description for Add constructor logic.
/// </summary>
public AuthorsCollection()
{

}

protected override void OnInsert(int index,object value)
{

}
}

[Simon Franklin]

"Simon Franklin" <simonfranklin@iperium.com> wrote:
>
>"Jay Glynn" <jlsglynn@hotmail.com> wrote:
>>You can either look at using ArrayList, it's dynamic and can grow as needed
>>or you can create your own collection class. If that is what you wish look
>>at using CollectionBase as your base class.
>>
>>"Ricardo" <rmendes@aksistemas.com.br> wrote in message
>>news:3d469a9e$1@10.1.10.29...
>>>
>>> I'm trying to create a mechanism of sales. I have a Sales class and an
>>Item
>>> class. The Sales contains a lot of items. So, how can I make it?
>>> If I use an array (public Item[] item) in the Sales class, I have to
give
>>> an inicial size for the array and this is bad (I don't know how many
items
>>> I will have).
>>>
>>
>>
>The following two classes show how to create a collection class that holds
>a list of Authors modify the code to your own design and enjoy.
>
>/// <summary>
> /// Summary description for the Author class.
> /// </summary>
> [Serializable]
> public class Author
> {
> /// <summary>
> /// Summary description for private String authorid;.
> /// </summary>
> private String authorid;
> /// <summary>
> /// Summary description for private String firstname;.
> /// </summary>
> private String firstname;
> /// <summary>
> /// Summary description for private String lastname;.
> /// </summary>
> private String lastname;
> /// <summary>
> /// Summary description for Property AuthorID .
> /// </summary>
> public String AuthorID
> {
> get
> {
> return authorid;
> }
> set
> {
> authorid = value;
> }
> }
> /// <summary>
> /// Summary description for Property FirstName .
> /// </summary>
> public String FirstName
> {
> get
> {
> return firstname;
> }
> set
> {
> firstname = value;
> }
> }
> /// <summary>
> /// Summary description for Property LastName .
> /// </summary>
> public String LastName
> {
> get
> {
> return lastname;
> }
> set
> {
> lastname = value;
> }
> }
> /// <summary>
> /// Summary description for Author().
> /// </summary>
> public Author()
> {
>
> }
> /// <summary>
> /// Summary description for Author(String authorid,String firstname,String
>lastname,AuthorAddress address).
> /// </summary>
> public Author(String authorid,String firstname,String lastname)
> {
> this.AuthorID = authorid;
> this.FirstName = firstname;
> this.LastName = lastname;
> }
> /// <summary>
> /// Summary description for Author(Author AuthorDetails).
> /// </summary>
> public Author(Author AuthorDetails)
> {
> this.AuthorID = AuthorDetails.AuthorID;
> this.FirstName = AuthorDetails.FirstName;
> this.LastName = AuthorDetails.LastName;
> }
> }
>/// <summary>
> /// Summary description for public class AuthorsCollection : System.Collections.CollectionBase
> /// </summary>
> [Serializable]
> public class AuthorsCollection : System.Collections.CollectionBase
> {
> /// <summary>
> /// Summary description for public Author this[int index].
> /// </summary>
> public Author this[int index]
>
> {
> get
> {
> return (Author) List[index];
> }
> set
> {
> List[index] = value;
> }
> }
> /// <summary>
> /// Summary description for public Author item(int index).
> /// </summary>
> public Author item(int index)
>
> {
> return (Author) List[index];
> }
>
> /// <summary>
> /// Summary description for public void Add(AssociateContentItem ContentItem).
> /// </summary>
> public void Add(Author AuthorItem)
> {
> List.Add(AuthorItem);
> }
>
> /// <summary>
> /// Summary description for public void Remove(int index).
> /// </summary>
> public void Remove(int index)
> {
> if (index > Count - 1 || index < 0)
> {
> ///
> }
> else
> {
> List.RemoveAt(index);
> }
> }
> /// <summary>
> /// Summary description for Add constructor logic.
> /// </summary>
> public AuthorsCollection()
> {
>
> }
>
> protected override void OnInsert(int index,object value)
> {
>
> }
> }
//Sorry forgot to show the code to implement the two classes.
//Create the AuthorsCollection class to hold the list of Authors.
AuthorsCollection AC = new AuthorsCollection();
//Create the Author class and set its properties.
Author BookAuthor = new Author();
BookAuthor.FirstName = "YourAuthorFirstName";
BookAuthor.LastName = "YourAuthorLastName";
BookAuthor.AuthorID = "YourAuthorID";
//Add the Author class to the collection
AC.Add(BookAuthor);
//Now convert a member of the collection to an XmlElement and add it to an
XmlDocument.
XmlDocument xDoc = new XmlDocument();
xDoc.LoadXml("<Authors></Authors>");
XmlNode xNode = xDoc.DocumentElement;
XmlElement MyAuthorElement = xDoc.CreateElement("Author");
//Access the AuthorsCollection by index value.
MyAuthorElement.SetAttribute("FirstName",AC.item(0).FirstName);
MyAuthorElement.SetAttribute("LastName",AC.item(0).LastName);
MyAuthorElement.SetAttribute("AuthorID",AC.item(0).AuthorID);
//Add the new Element to the XmlDocument;
xNode.AppendChild((XmlNode)MyAuthorElement);
//The output should look something like the following;
//<Authors>.
// <Author FirstName="YourAuthorFirstName" LastName="YourAuthorLastName"
AuthorID="YourAuthorID" />
//</Authors>.
//Also remember that because the AuthorsCollection is derived from System.Collections.CollectionBase
//it can be accessed using foreach.
//For example
foreach (Author MyAuthor in AC)
{
Console.WriteLine(MyAuthor.FirstName);
}

[David Chu]

How about to add a key feature to a collection so that each item can be added
to the collection by a key, or item in the collection can be referenced by
a key?

Example:

AC.Add ( authore, "key1");
string name = AC.Item("Key1").FirstName;

David Chu

[Jay Glynn]

Then you would want to use DictionaryBase or implement IDictionary.


"David Chu" <chudq@hotmail.com> wrote in message
news:3d6265b3$1@10.1.10.29...
>
> How about to add a key feature to a collection so that each item can be
added
> to the collection by a key, or item in the collection can be referenced by
> a key?
>
> Example:
>
> AC.Add ( authore, "key1");
> string name = AC.Item("Key1").FirstName;
>
> David Chu

[David Chu]

I tried to build a collection based on DictionaryBase. The attachment is the
code for the class and test codes.

It works fine except some points:

1. It does not support index such as:
Widget w = wCol1.Item(0);
You have to use key to get item:
Widget w = wCol1.Item("1");
2. The order of retrieving items from collection in foreach loop is not the
order of items added. For example, I added widget object in the order with
Name properties of "One", "Two" and "Three". However, I got the result from
foreach loop is widget with Names of "Two", "Three" and "Two".

I don't understand the order of items in DictionaryBase collection.


// ======================== Class definition, collection base on Widget class

public class WidgetCollectionWKey : System.Collections.DictionaryBase
{
// Restricts to Widget types, items that can be added to the collection

public void Add(object key, Widget aWidget )
{
Dictionary.Add(key, aWidget );
}

public void Remove(object key)
{
// Check to see if there is a widget at the supplied index.
if ( key != null )
{
// If the DictionaryBase does not contain an element with the specified
key,
// the DictionaryBase remains unchanged. No exception is thrown.
Dictionary.Remove( key );
}
}

public Widget Item(object key)
{
// The appropriate item is retrieved from the List object and
// explicitly cast to the Widget type, then returned to the
// caller.
return (Widget) Dictionary[ key ];
}

public bool ItemExit ( object key )
{
bool bRet = true;

try
{
bRet = ( Dictionary.Contains( key ) );
}
catch { bRet = false; }
return bRet;
}

}

// ============ Testing codes:

WidgetCollectionWKey wCol1 = new WidgetCollectionWKey();

wCol1.Add ("2", new Widget("Two", "3") );
wCol1.Add ("1", new Widget("One", "2") );
wCol1.Add ("3", new Widget("Three", "1") );
wCol1.Add ("4", null );

foreach (DictionaryEntry d in wCol1 )
{
Widget w = (Widget) d.Value;
if ( w != null )
Console.WriteLine ("Item: {0}", w.Name );
}