The posters with the .net 3.5 Framework Namespaces have been updated. You can download the new versions in different formats by clicking on the links below.

Introduction

Dijkstra was a Dutch computer scientist who invented a fast and simple way to calculate the shortest path between two points. Many examples I have found on the Internet implement that algorithm but none of them have done it in an Object Oriented way. So I thought of making my own.

Background

Information about Dijkstra can be found here.

Using the Code

The code contains two Project classes:

1. GUI: Shows the information visually
   • To add locations, click on the 'Add Location' button and then click on the map where you want to add locations.
   • To add routes, click on the 'Add Location' button to deactivate the add location, then click on a start location, then click on a end location. The weight of the route can be configured on top.
2. RouteEngine: Calculates the route

I will only go into details about the RouteEngine. How the UI is handled is not so important for this article but if you need information about it, you can always ask.

Project RouteEngine

1. Connection: This class holds the information about the connection between two dots. This is a one directional connection from A (the startpoint is visually shown with a dot) to B with a specific weight attached.
2. Location: Just a location (for example 1).
3. RouteEngine: This class will calculate all routes from one given startPoint.
4. Route: This class holds the information about a route between two points (generated with the RouteEngine class).

Location

The most simple class. It only holds a name to display.

Connection

This class contains two Location objects and a weight.

public Connection(Location a, Location b, int weight)
{
    this._a = a;
    this._b = b;
    this._weight = weight;
}

Route

This class contains a route. It has only a list of connections and the total weight. This class is generated by the route engine.

Route Engine

This is the class that drives the component. The algorithm is as follows:

1. Set the startPosition as active
2. Set the total weight to all routes to infinite
3. Iterate through all connections of the active position and store their weight if their weight is smaller than their current weight
4. Set the active position as used
5. Set the nearest point (on whatever location) that isn't used as active
6. Repeat 3, 4, 5 until all positions are used

The following method will perform all these steps (and some extra checking and thinking). The Dictionary returned is a list of destination locations and the corresponding route to each destination location.

• Download demo project - 11.23 KB
• Download source - 56.63 KB

Tired of querying in antiquated SQL?

Well, you don't have to!  LINQPad lets you interactively query SQL databases in a modern query language: LINQ.  Kiss goodbye to SQL Management Studio!

LINQPad supports everything in C# 3.0 and Framework 3.5:

• LINQ to SQL
• LINQ to Objects
• LINQ to XML

LINQPad is also a terrific tool for learning LINQ: it comes preloaded with 200 examples from the recently released C# 3.0 in a Nutshell.  There's no better way to experience the coolness of LINQ and functional programming.

LINQPad is free and needs no installation: just download and run.  The executable is only 1MB and is self-updating.

© 2007 Joseph Albahari

Once you have the ASP.NET 3.5 Extensions CTP release installed, you can use VS 2008 or the free Visual Web Developer 2008 Express to create a new Web Site or Web Application Project that has the ASP.NET dynamic data support enabled:

Learning More

The above walk-through only touches on a few of the scenarios and capabilities you can enable with ASP.NET Dynamic Data Projects.  To learn more:

1. Watch David's webcast
2. Check out the ASP.NET Dynamic Data QuickStarts
3. Subscribe to David Ebbo's, Scott Hunter's, and Marcin Dobosz's blogs
4. Visit the ASP.NET Dynamic Data Forum to ask questions