Re: Data Object Collection Inheritance

From: Steve Willcock (steve_at_N-O-S-P-A-Mwillcockconsulting.com)
Date: 08/10/04 

Date: Tue, 10 Aug 2004 23:13:51 +0100

George, you can fix this by setting the Add method in the base collection
class to be virtual and then overriding it in the SubClass - i.e.

public override int Add(object value)

{

SubClassData[] arrCollection = new SubClassData[0];

arrCollection = (SubClassData[])this.DataCollection.Clone();

this.DataCollection = new SubClassData[arrCollection.Length + 1];

arrCollection.CopyTo(this.DataCollection,0);

this.DataCollection[this.DataCollection.Length - 1] = (SubClassData)value;

return 1;

}

On another note, you might want to have a look at the CollectionBase class
which helps to simplify a lot of the code you're writing here -
http://www.csharphelp.com/archives/archive256.html this is an example of
it's usage. 

-- 
Steve Will*** (MCSD for Microsoft.NET)
http://www.willcockconsulting.com/
"George Prado" <George Prado@discussions.microsoft.com> wrote in message
news:7DF4DC7C-16DD-4542-9963-867571D1B963@microsoft.com...
> I am new to the collections objects in C# and have a question to ask of
those
> who know how collections work in list boxes. I have put together a sample
app
> to show what is going on.  My issue is I have a collection of data objects
> and I cannot link inherited properties to my list control.  If the
property
> lies in the base data object I can get it but not if it is in the
inherited
> object.  All those properties are invisible to the list control. Load my
code
> below for an example of what I am talking about.  Any help would be
greatly
> appreciated!  I am also open to suggestion if any one knows of a better
way
> to create business object.
>
> George Prado
>
> Form1.cs:
>
> using System;
> using System.Drawing;
> using System.Collections;
> using System.ComponentModel;
> using System.Windows.Forms;
> using System.Data;
>
> namespace CollectionSample
> {
> /// <summary>
> /// Summary description for Form1.
> /// </summary>
> public class Form1 : System.Windows.Forms.Form
> {
> private System.Windows.Forms.ListBox listBox1;
> private System.Windows.Forms.Button cmdID;
> private System.Windows.Forms.Button cmdText;
> /// <summary>
> /// Required designer variable.
> /// </summary>
> private System.ComponentModel.Container components = null;
>
> public Form1()
> {
> //
> // Required for Windows Form Designer support
> //
> InitializeComponent();
>
> //
> // TODO: Add any constructor code after InitializeComponent call
> //
> }
>
> /// <summary>
> /// Clean up any resources being used.
> /// </summary>
> protected override void Dispose( bool disposing )
> {
> if( disposing )
> {
> if (components != null)
> {
> components.Dispose();
> }
> }
> base.Dispose( disposing );
> }
>
> #region Windows Form Designer generated code
> /// <summary>
> /// Required method for Designer support - do not modify
> /// the contents of this method with the code editor.
> /// </summary>
> private void InitializeComponent()
> {
> this.listBox1 = new System.Windows.Forms.ListBox();
> this.cmdID = new System.Windows.Forms.Button();
> this.cmdText = new System.Windows.Forms.Button();
> this.SuspendLayout();
> //
> // listBox1
> //
> this.listBox1.Location = new System.Drawing.Point(40, 16);
> this.listBox1.Name = "listBox1";
> this.listBox1.Size = new System.Drawing.Size(240, 173);
> this.listBox1.TabIndex = 0;
> //
> // cmdID
> //
> this.cmdID.Location = new System.Drawing.Point(24, 216);
> this.cmdID.Name = "cmdID";
> this.cmdID.Size = new System.Drawing.Size(112, 23);
> this.cmdID.TabIndex = 1;
> this.cmdID.Text = "Link to ID";
> this.cmdID.Click += new System.EventHandler(this.cmdID_Click);
> //
> // cmdText
> //
> this.cmdText.Location = new System.Drawing.Point(168, 216);
> this.cmdText.Name = "cmdText";
> this.cmdText.Size = new System.Drawing.Size(128, 23);
> this.cmdText.TabIndex = 2;
> this.cmdText.Text = "Link to AnotherColumn";
> this.cmdText.Click += new System.EventHandler(this.cmdText_Click);
> //
> // Form1
> //
> this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
> this.ClientSize = new System.Drawing.Size(328, 266);
> this.Controls.Add(this.cmdText);
> this.Controls.Add(this.cmdID);
> this.Controls.Add(this.listBox1);
> this.Name = "Form1";
> this.Text = "Form1";
> this.Load += new System.EventHandler(this.Form1_Load);
> this.ResumeLayout(false);
>
> }
> #endregion
>
> /// <summary>
> /// The main entry point for the application.
> /// </summary>
> [STAThread]
> static void Main()
> {
> Application.Run(new Form1());
> }
>
> private void Form1_Load(object sender, System.EventArgs e)
> {
> objNewCollection = new SubClassCollection();
> this.listBox1.DataSource = objNewCollection.Collection;
> }
>
> private CollectionSample.SubClassCollection objNewCollection;
>
> private void cmdID_Click(object sender, System.EventArgs e)
> {
> this.listBox1.DisplayMember = "ID";
> }
>
> private void cmdText_Click(object sender, System.EventArgs e)
> {
> this.listBox1.DisplayMember = "AnotherColumn";
> }
> }
>
> public abstract class BaseData
> {
> protected System.Data.DataRow drCurrent;
>
> public BaseData()
> {
>
> }
>
> public int ID
> {
> get
> {
> //return (int)drCurrent["id"];
> return 1;
> }
> }
> /*All base functionality for data objects
> *
> *
> *
> */
> }
>
> public sealed class SubClassData : CollectionSample.BaseData
> {
> public SubClassData()
> {
> //load data row with data
> }
>
> public string AnotherColumn
> {
> get
> {
> //return (string)this.drCurrent["AnotherColumn"];
> return "I Don't Get This Text In The List";
> }
> }
> /*All specific functionality for data objects
> *
> *
> *
> */
> }
>
> public abstract class BaseDataCollection : System.Collections.IEnumerable,
> System.Collections.IList
> {
> protected BaseData[] DataCollection;
>
> public BaseDataCollection()
> {
>
> }
>
> public BaseData[] Collection
> {
> get
> {
> return this.DataCollection;
> }
> }
>
> #region IEnumerable Members
>
> public System.Collections.IEnumerator GetEnumerator()
> {
> return new DataEnumerator(this);
> }
>
> #endregion
>
> #region IList Members
>
> public bool IsReadOnly
> {
> get
> {
> // TODO:  Add BaseDataCollection.IsReadOnly getter implementation
> return false;
> }
> }
>
> public object this[int index]
> {
> get
> {
> return this.DataCollection[index];
> }
> set
> {
> // TODO:  Add BaseDataCollection.this setter implementation
> }
> }
>
> public void RemoveAt(int index)
> {
> // TODO:  Add BaseDataCollection.RemoveAt implementation
> }
>
> public void Insert(int index, object value)
> {
> // TODO:  Add BaseDataCollection.Insert implementation
> }
>
> public void Remove(object value)
> {
> // TODO:  Add BaseDataCollection.Remove implementation
> }
>
> public bool Contains(object value)
> {
> // TODO:  Add BaseDataCollection.Contains implementation
> return false;
> }
>
> public void Clear()
> {
> // TODO:  Add BaseDataCollection.Clear implementation
> }
>
> public int IndexOf(object value)
> {
> // TODO:  Add BaseDataCollection.IndexOf implementation
> return 0;
> }
>
> public int Add(object value)
> {
> BaseData[] arrCollection = new BaseData[0];
> arrCollection = (BaseData[])this.DataCollection.Clone();
> this.DataCollection = new BaseData[arrCollection.Length + 1];
> arrCollection.CopyTo(this.DataCollection,0);
> this.DataCollection[this.DataCollection.Length - 1] = (BaseData)value;
> return 1;
> }
>
> public bool IsFixedSize
> {
> get
> {
> // TODO:  Add BaseDataCollection.IsFixedSize getter implementation
> return false;
> }
> }
>
> #endregion
>
> #region ICollection Members
>
> public bool IsSynchronized
> {
> get
> {
> // TODO:  Add BaseDataCollection.IsSynchronized getter implementation
> return false;
> }
> }
>
> public int Count
> {
> get
> {
> return this.DataCollection.Length;
> }
> }
>
> public void CopyTo(Array array, int index)
> {
> // TODO:  Add BaseDataCollection.CopyTo implementation
> }
>
> public object SyncRoot
> {
> get
> {
> // TODO:  Add BaseDataCollection.SyncRoot getter implementation
> return null;
> }
> }
>
> #endregion
>
> #region Data Enumerator
>
> private class DataEnumerator : System.Collections.IEnumerator
> {
> private int position = -1;
> private BaseDataCollection Items;
>
> public DataEnumerator(BaseDataCollection Collection)
> {
> this.Items = Collection;
> this.position = -1;
> }
>
> #region IEnumerator Members
>
> public void Reset()
> {
> this.position = -1;
> }
>
> public object Current
> {
> get
> {
> return this.Items[this.position];
> }
> }
>
> public bool MoveNext()
> {
> bool boolReturns = false;
> if(!this.position.Equals(this.Items.Count))
> {
> this.position++;
> boolReturns = true;
> }
> return boolReturns;
> }
>
> #endregion
> }
>
> #endregion
> }
>
> public sealed class SubClassCollection : BaseDataCollection
> {
> public SubClassCollection()
> {
> this.DataCollection = new SubClassData[0];
> this.LoadCollection();
> }
>
> private void LoadCollection()
> {
> //Get the data objects you want in collection
> this.Add(new SubClassData());
> this.Add(new SubClassData());
> this.Add(new SubClassData());
> this.Add(new SubClassData());
> this.Add(new SubClassData());
> //add as many business objects as needed in collection.
> }
> }
> }
>
>
>