C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    abstract class A
    {    }

    class B : A
    {    }

    class C : A
    {    }


    class ClassX
    {
        static void DoStuff()
        {
            List<B> listB = new List<B>();
            List<C> listC = new List<C>();

            List<A>[] arrayOfLists = new List<A>[2];

            arrayOfLists[0] = listB;//Error	1	Cannot implicitly convert type 'System.Collections.Generic.List<ConsoleApplication1.B>'
            arrayOfLists[1] = listC;//Error	2	Cannot implicitly convert type 'System.Collections.Generic.List<ConsoleApplication1.C>'

            arrayOfLists[0] = listB.Cast<A>().ToList();//Subsequent changes in list B are not seen an arrayoflists because a new object is created

            List<List<A>> listOfLists = new List<List<A>>();
            listOfLists.Add(listB);//Error	4	Argument 1: cannot convert from 'System.Collections.Generic.List<ConsoleApplication1.B>' to 'System.Collections.Generic.List<ConsoleApplication1.A>'
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Text;
using System.Windows.Forms;
using iAnywhere.Data.UltraLite;
using System.Collections;

namespace ChannMap
{
    public partial class Form1 : Form
    {
        private string strChan;
        private string strFreq;
        private string strName;
        private string strMapChan;
        private string strTemp;
        private string [] strArraylist=new string [1000];
        static int i = 0; //index for strArraylist
        private ULConnection ConnUL = new ULConnection();
        private ULDataAdapter myDataAdapter = new ULDataAdapter();
        private void Form1_Load(object sender, System.EventArgs e)
        {
            fnGetConnectedToDatabase();
        }
        public Form1()
        {
            InitializeComponent();
            
        }
        private void fnGetConnectedToDatabase()
        {
            try
            {
                String dbf = "\\Program Files\\ChannMap\\ChannMap.udb";

                if (System.IO.File.Exists(dbf))
                {
                    ConnUL.ConnectionString = "dbf=" + dbf + ";cache_size=1M";
                    if (ConnUL.State != ConnectionState.Open)
                    {
                        ConnUL.Open();
                    }
                    ConnUL.DatabaseID = 1000;
                }
                else
                {
                    MessageBox.Show("Database is not available", "Error");
                    Application.Exit();
                }
            }
            catch (System.Exception t)
            {
                MessageBox.Show(t.Message, "Connection failed");
                return;
            }
            string sqlStr = "SELECT * FROM Names;";
            			myDataAdapter = new ULDataAdapter(sqlStr,ConnUL);

			//Instantiate a DataSet
			DataSet myDataset = new DataSet();
			
			// Populate the data table "Names"
			myDataset.Clear();
			myDataAdapter.Fill(myDataset,"Names");		
			
			foreach (DataRow myRow in myDataset.Tables["Names"].Rows)
			{
				strChan =(string) myRow["chan"];
                strFreq = (string)myRow["freq"];
				strMapChan=(string) myRow["mpchan"];
                strName=(string) myRow["name"];

                strTemp=strChan+"*"+strFreq+"*"+strMapChan+"*"+strName;
				//put strTemp into string strArraylist with int i(index for strArraylist)
				strArraylist[i++]=strTemp;
				//display in the ComboBox only strStudentID
				comboChanName.Items.Add(strName);
			}
			// Close the connection to the database.
			ConnUL.Close();

        }
        private void comboChanName_SelectedIndexChanged(object sender, System.EventArgs e)
        {
            string delimstr = "*";
            char [] delimeter = delimstr.ToCharArray();
            string [] splitstr = null;

            splitstr = strArraylist[this.comboChanName.SelectedIndex].Split(delimstr, 4);
            //Now assign the data from splitstr to TextBoxes
            textBox1.Text = splitstr[0];
            textBox2.Text = splitstr[1];
           textBox3.Text = splitstr[2];
           textBox4.Text = splitstr[3];

        }///////////////////////////////////////////////


    }
}

using System.IO;
public void DeleteAfterCopyingOriginalImageFile(string strOriginalJpeg)
{
   // Create "JpegTemp" sub-folder at temporary directory path
   string strTempFolder = System.IO.Path.Combine(System.IO.Path.GetTempPath(), "JpegTemp");
   if (!Directory.Exists(strTempFolder))
   {
      DirectoryInfo directory = Directory.CreateDirectory(strTempFolder);
      directory.Attributes = directory.Attributes | FileAttributes.Hidden;
   }

   // Get the temp file path
   string strTempJpeg = System.IO.Path.Combine(strTempFolder, "TempImage.jpg");

   // Copy the original JPEG as below
   if (!File.Exists(strTempJpeg))
   {
      File.Copy(strOriginalJpeg, strTempJpeg);
   }

   // Open the "TempImage.jpg" file in default viewer. Doing this lock the original jpeg file.
   // Don't know why? It is creating problem for me.
   Process.Start(strTempJpeg);

   // Delete original JPEG file. Since the file is locked in above step, application throws exception
   // "File being used by some other process" and then application crashes.
   File.Delete(strOriginalJpeg);
}