Data Object Collection Inheritance

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From: George Prado (Prado_at_discussions.microsoft.com)
Date: 08/10/04 

Date: Tue, 10 Aug 2004 11:57:03 -0700

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.
                }
        }
}

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