How to programatically bind a value to a parameter in a ObjectDataSource

I'm making a guestbook, and one of the values that I'm inserting into the database is the IP address of the user. To get the IP address to bind to the parameter "IP" I added a event that is raised when "Inserting" to the objectdatasource.

From here I just add the value:

protected void ObjectDataSource1_Inserting(object sender, ObjectDataSourceMethodEventArgs e)
{
e.InputParameters["IP"] = Request.UserHostAddress;
}

File Download in ASP.Net

Ok, so I'm making my own site and what I am doing is allowing users on my website to upload and download files. These files are placed into my sql-server database. I was having trouble getting the Response.Write to work, so I went to Response.OutputStream.Write instead.

So on my download page I have:

protected void Page_Load(object sender, EventArgs e)
{
String filepath =
Request.Params.Get("Author") + "-" + Request.Params.Get("Title") + ".mp3";
if
(filepath.Length != 0)
{
Stream readStream =
MusicManager.GetSong(Int32.Parse(Request.Params.Get("file")));
int Length =
256;
Response.Clear();
Response.ContentType =
"application/octet-stream";
Response.AddHeader("Content-Disposition",
"attachment; filename=\"" + filepath + "\"");
Response.Flush();
Byte[]
buffer = new Byte[Length];
int bytesRead = readStream.Read(buffer, 0,
Length);
while (bytesRead > 0)
{
Response.OutputStream.Write(buffer,
0, bytesRead);
bytesRead = readStream.Read(buffer, 0,
Length);
}
Response.End();
readStream.Close();
}
}

Of course I have a page that sends in the query string with the necessary info

This seems all simple when it starts working, but it took me 2 hours to get the file to download correctly.

A good source of information on de-bugging IIS 7 errors

http://mvolo.com/blogs/serverside/archive/2007/07/26/Troubleshoot-IIS7-errors-like-a-pro.aspx

Good source on optimizing SQL Server 2005

http://technet.microsoft.com/en-us/sqlserver/bb331794.aspx

Interview question: What structure would you use to represent shapes in a database?

OK, A few months ago, my friend told me of an interview question that I found interesting. The question that was given to him, paraphrasing: "If you had to set up a database to hold shapes, what would your table structure look like?". The point of the question was for him to convert the concept of a class shape that might be used in an object oriented language to be converted to a database structure. Which is why I was stuck on this question, with no simple straight forward solution.

I then started thinking about this question, again. The idea of the question was to see what tables and columns would you set up to make this feasible. I wanted an easy solution with minimal work, so I avoided the polymorphism concept and went to a simpler definition of a shape (polygon).

I figure I would make 1 table called SHAPE with 2 columns and make the assumption that the shapes are defined as "simple polygons":


ID int, COORDINATES varchar





The ID is obviously the primary key for each shape.


The Coordinates is a order list of Cartesian coordinates going counter-clockwise.

Now, given a shape, the most common questions asked would be what is the perimeter and area of said shape. I could easily make 2 store procedures to find the perimeter and area.

To figure out the perimeter, I just need to add up the distance from each point, simple enough.

To figure out the area of the polygon, I knew there had to be a formula that would do this for me, and thanks to wikipedia I found one:





"The formula was described by Meister in 1769 and by Gauss in 1795. It can be verified by dividing the polygon into triangles".


I was looking around, to see if others seen this question. I did find something similar at http://lists.mysql.com/mysql/207823

If I needed to query the table for certain shapes, then it would be good to add an additional column called: Points int

So, if I needed to query the table for triangles only then I can do a search on points = 3.

Efficient use of Iterators and Delegates

This is a good read. It shows how to effectually use iterators to make garbage collection efficient and to lower memory usage. It also shows how to use delegates to also improve on this concept.

http://msdn2.microsoft.com/en-us/vcsharp/bb264519.aspx

Take the initial uneffecient example:

// First attempt:
public List PeopleIKnowInNewYork()
{
IEnumerable newYorkNumbers = PhoneBook.FindListFor(“New York”);
List peopleIKnow = new List();

foreach ( PhoneBookEntry ph in newYorkNumbers)
{
string name = string.Format(“{0} {1}”, ph.FirstName,
ph.LastName);

if ( RecognizePerson( name ) )
peopleIKnow.Add(name);
}

return peopleIKnow;
}

// Fifth attempt:public

IEnumerable PeopleIKnowInNewYork()
{
IEnumerable newYorkNumbers =
PhoneBook.FindListFor(“New York”);
IEnumerable names = Transform(newYorkNumbers,
delegate(PhoneEntry entry)
{
return string.Format(“{0} {1}”, entry.FirstName, entry.LastName);
});
return Filter(names,
delegate(string name)
{
return RecognizePerson(name);
}
);
}

LINQ and AI?

Well, LINQ is something new to both VB and C# in Visual Studio 8 that allows you to query the data. The data can be XML, ADO.NET, DataSet, or objects. An example of the LINQ format:

var locals = (from c in customers
where c.ZipCode == 91822
select new { FullName = c.FirstName + “ “ +
c.LastName, HomeAddress = c.Address})
.Count();

What I find really interesting about the possibility of using LINQ, is the idea that the program can look at itself in an evaluation. If you add some artificial intelligence, this idea can be a great help in developing programs that can prove themselves correct in logic. I even think, that this concept can be used, with lots of time and planning, to develop a program that can write other programs given a set of parameters and acceptable outcomes.

The concept of using a database like language in a structure language is a very nice concept. If LINQ could be used to select all number of the type Int32 to represent integer numbers, would be something fun to play with. On this subject I might be a little too much in the dream world at the momement, but I do look forward to the possibilities.

Some sources on LINQ:

http://msdn.microsoft.com/msdnmag/issues/07/06/CSharp30/
http://blogs.msdn.com/charlie/archive/2007/07/26/visual-studio-2008-beta-2-released.aspx

Some info on Lambda Calculus:

http://en.wikipedia.org/wiki/Typed_lambda_calculus

Quick Reference: Raise Events in C#

Just wanted to put this down for a quick reference to remember how to raise an event in C#:

Declare:

private delegate void OnMouseOverDelegate(object
sender, System.EventArgs e);
private event OnMouseOverDelegate OnMouseOver;

After InitializeComponent(); :

this.OnMouseOver += new OnMouseOverDelegate(my_MouseHover);

Function:

private void
my_MouseHover(object sender, System.EventArgs e)
{
}