C#

using System;
using System.Collections.Generic;

public class Example
{
	public static void Main()
	{
		// Create a new sorted list of strings, with string
		// keys.
		SortedList<string, string> openWith = 
			new SortedList<string, string>();

		// Add some elements to the list. There are no 
		// duplicate keys, but some of the values are duplicates.
		openWith.Add("txt", "notepad.exe");
		openWith.Add("bmp", "paint.exe");
		openWith.Add("dib", "paint.exe");
		openWith.Add("rtf", "wordpad.exe");

		// The Add method throws an exception if the new key is 
		// already in the list.
		try
		{
			openWith.Add("txt", "winword.exe");
		}
		catch (ArgumentException)
		{
			Console.WriteLine("An element with Key = \"txt\" already exists.");
		}

		// The Item property is another name for the indexer, so you 
		// can omit its name when accessing elements. 
		Console.WriteLine("For key = \"rtf\", value = {0}.", 
			openWith["rtf"]);

		// The indexer can be used to change the value associated
		// with a key.
		openWith["rtf"] = "winword.exe";
		Console.WriteLine("For key = \"rtf\", value = {0}.", 
			openWith["rtf"]);

		// If a key does not exist, setting the indexer for that key
		// adds a new key/value pair.
		openWith["doc"] = "winword.exe";

		// The indexer throws an exception if the requested key is
		// not in the list.
		try
		{
			Console.WriteLine("For key = \"tif\", value = {0}.", 
				openWith["tif"]);
		}
		catch (KeyNotFoundException)
		{
			Console.WriteLine("Key = \"tif\" is not found.");
		}

		// When a program often has to try keys that turn out not to
		// be in the list, TryGetValue can be a more efficient 
		// way to retrieve values.
		string value = "";
		if (openWith.TryGetValue("tif", out value))
		{
			Console.WriteLine("For key = \"tif\", value = {0}.", value);
		}
		else
		{
			Console.WriteLine("Key = \"tif\" is not found.");
		}

		// ContainsKey can be used to test keys before inserting 
		// them.
		if (!openWith.ContainsKey("ht"))
		{
			openWith.Add("ht", "hypertrm.exe");
			Console.WriteLine("Value added for key = \"ht\": {0}", 
				openWith["ht"]);
		}

		// When you use foreach to enumerate list elements,
		// the elements are retrieved as KeyValuePair objects.
		Console.WriteLine();
		foreach( KeyValuePair<string, string> kvp in openWith )
		{
			Console.WriteLine("Key = {0}, Value = {1}", 
				kvp.Key, kvp.Value);
		}

		// To get the values alone, use the Values property.
		IList<string> ilistValues = openWith.Values;

		// The elements of the list are strongly typed with the 
		// type that was specified for the SorteList values.
		Console.WriteLine();
		foreach( string s in ilistValues )
		{
			Console.WriteLine("Value = {0}", s);
		}

		// The Values property is an efficient way to retrieve
		// values by index.
		Console.WriteLine("\nIndexed retrieval using the Values " +
			"property: Values[2] = {0}", openWith.Values[2]);

		// To get the keys alone, use the Keys property.
		IList<string> ilistKeys = openWith.Keys;

		// The elements of the list are strongly typed with the 
		// type that was specified for the SortedList keys.
		Console.WriteLine();
		foreach( string s in ilistKeys )
		{
			Console.WriteLine("Key = {0}", s);
		}

		// The Keys property is an efficient way to retrieve
		// keys by index.
		Console.WriteLine("\nIndexed retrieval using the Keys " +
			"property: Keys[2] = {0}", openWith.Keys[2]);

		// Use the Remove method to remove a key/value pair.
		Console.WriteLine("\nRemove(\"doc\")");
		openWith.Remove("doc");

		if (!openWith.ContainsKey("doc"))
		{
			Console.WriteLine("Key \"doc\" is not found.");
		}
	}
}

/* This code example produces the following output:

An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe

Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe
Key = rtf, Value = winword.exe
Key = txt, Value = notepad.exe

Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = hypertrm.exe
Value = winword.exe
Value = notepad.exe

Indexed retrieval using the Values property: Values[2] = winword.exe

Key = bmp
Key = dib
Key = doc
Key = ht
Key = rtf
Key = txt

Indexed retrieval using the Keys property: Keys[2] = doc

Remove("doc")
Key "doc" is not found.
*/

Luis Alonso Ramos
Intelectix
Chihuahua, Mexico

irumamir wrote:

Yes I am required to usr .NET 1.1.

...
  
// Reference: System.Design.dll
using System.Drawing.Design;
using System.Windows.Forms.Design;
  
...
  
internal class MyFileNameEditor : FileNameEditor
{
  protected override void InitializeDialog(OpenFileDialog openFileDialog)
  {
    base.InitializeDialog (openFileDialog);
    openFileDialog.Filter = "JPEG Files (*.jpg)|*.jpg|All Files (*.*)|*.*";
  }
}
  
...
  
[EditorAttribute(typeof(MyFileNameEditor), typeof(UITypeEditor))]
public string PictureBoxBackgroundImage
{
  get { return m_bgImagePath; }
  set
  {
    m_bgImagePath = value;
    Image bgImage = Image.FromFile(m_bgImagePath);
    // should do some Image creation error checking here
    this.thePictureBox.BackgroundImage = bgImage;
  }
}

kumar.bs wrote:

sorry the message heading should be "Important design partterns in C# solutions"

Microsoft patterns & practices are Microsoft's recommendations for how to 
design, develop, deploy, and operate architecturally sound applications for 
the Microsoft application platform.