Get Rid.

Wisdom.

DateDiff

Recently, I had to work out the number of months between two arbitrary dates. In C# this is a bit of a challenge, simply because DateTime.Subtract(DateTime) returns a TimeSpan, which does not have a Months property.

This is because TimeSpan doesn't know which months it would be referring to. Specifically, to know how many months there are in a date range you need to count each month index from date A to date B. Problem being, if you don't know those arbitrary dates - you only have a count of days - how many months does that range cover?

Example: How many months does 30 days represent? Answer: 1.

Wrong.

Why?... Because if we are talking about February, it's two months. If we're talking about August it's not a whole month.

The solution is to take into account the specific dates being used in the subtraction and count their months, unfortunately. Yeah, I don't want to write that code either.

However, for the C#'ers among us, there is a solution. VB has a DateDiff class which can do this for you. Just use the Microsoft.VisualBasic namespace and the static DateDiff method, as I found out here:

• http://valcsgal.blogspot.com/2005/01/datediff-in-c.html

Here's a post about writing your own:

• http://aspcode.net/c-datediff

DataView, DataTable, Unique, Select And Filters

Found this awesome little cheat/info page on DataView et al:

• http://www.csharp-examples.net/dataview-rowfilter/

You Had Me At Brains And Squeegees

The Register: iPad Apps Galore

The Register has pulled together a collection of iPad apps for geeks, techies and web pros...

• SysAdmins
• Training and Editors
• Web Tools

LINQ2SQL Transaction

A good thread to read on LINQ to SQL transactions, centred on commits and rollbacks:

• http://stackoverflow.com/questions/542525/transactionscope-vs-transaction-in-linq2sql

Your Anonymous Survey Said...

You Don't Trust... Oh.

Why Not? "Wave-Enabled" Google Email Server

I was thinking that it's a shame that Google didn’t take the Wave, build it into their email server and have just an option that let you “email in real time”, ie: any email on their system could be seen to be edited in real time (as wave showed) but in the gmail editor.

The major work would be in the server, so that it is still an email system, exchange compatible and all, but also makes this new function available. Hopefully, people would use it more and more as rapid email repliers discover they are responding quickly.

Perhaps Google could then market their own email server as “Wave-enabled, MS Exchange-compatible”.

So simple really – read this:

• http://www.theregister.co.uk/2010/08/20/google_wave_lessons_learned/

ImageButton Without A SRC Value Causes GET Request!

Situation:

Click submit on a submit button.

Page posts back with IsPostBack == true.

Browser shows page render.

Problem:

Server (in debug mode) shows another request perform, this time a GET, so IsPostBack == false.

Evidence:

An ImageButton was on the page with no SRC attribute at all. This caused the browser (so far happening in (Windows...) Chrome, Firefox and (MAC...) Safari to resolve the URL of the image, for the image button, to be the same as the page the button is sitting on. The request for this then causes a standard GET request to the page and IsPostBack becomes false again.

Solution:

Remove the image button or give it a valid src attribute url.

Result:

Happy developer.

Javascript: Finding All The Properties Of A JScript Object

Just a little function to dump out into an alert all the properties, methods, etc of any javascript object...

function listout(obj) {

var keys;

for (var key in obj) {

keys += key + ' , ';

}

alert(keys);

}

I Found The Google

LINQ2SQL Exception: The query contains references to items defined on a different data context

When getting the exception

The query contains references to items defined on a different data context.

Check that the context object being used for each 'from' and 'join', etc, within LINQ statements is not a new object but the same one being re-used!

• http://stackoverflow.com/questions/3478148/two-linq-data-contexts-proving-a-problem

JQuery

A few JQuery links:

• JQuery site:
  http://jquery.com/
• JQuery UI building:
  http://jqueryui.com/
• 20 Advanced JQuery effects:
  http://www.webdesignerdepot.com/2010/07/20-demos-showing-advanced-jquery-effects/
• Setting cookies with JQuery:
  http://www.electrictoolbox.com/jquery-cookies/

Reset The Primary Key Of A Table

Lets say you've got 28 rows in your table but because you've been doing a lot of inserts and rollbacks the next key to be inserted is much higher than your highest primary key. This would be a problem if you've done a lot of inserts and have maybe reached the maximum value of the int type being used as the primary key field type.

You would want to reset the index (as all primary keys are special indices) like this:

DBCC CHECKIDENT ({tablename}, reseed, {number})

Don't make my initial mistake and think that the 'reseed' in the middle there is a place holder for a value - it isn't. Just leave it as is; it's a command. The operation is called reseeding, not resetting - but that will be all academic to most of us.

References:

• Insert:
  http://msdn.microsoft.com/en-us/library/ms174335.aspx
  http://www.google.co.uk/search?sourceid=chrome&ie=UTF-8&q=t-sql+insert
• Rollback:
  http://msdn.microsoft.com/en-us/library/ms181299.aspx
  http://www.google.co.uk/search?hl=en&q=t-sql+rollback&aq=f&aqi=g2g-c2g1&aql=&oq=&gs_rfai=
• DBCC CHECKIDENT:
  http://msdn.microsoft.com/en-us/library/ms176057.aspx
  http://www.google.co.uk/search?sourceid=chrome&ie=UTF-8&q=DBCC+CHECKIDENT
• Data type maximum values:
  http://www.tsqltutorials.com/datatypes.php
  http://www.google.co.uk/search?sourceid=chrome&ie=UTF-8&q=t-sql+int+maximum+value
• Pinal Dave:
  http://blog.sqlauthority.com/2007/03/15/sql-server-dbcc-reseed-table-identity-value-reset-table-identity/

LINQ: NOT IN / NOT EXISTS

So, while trying to get a fairly straight forward (I thought) select ... from ... where ... not in (...) I found that there is not really an equivalent in LINQ, or so I thought...

Read the solution here:

• http://programminglinq.com/blogs/marcorusso/archive/2008/01/14/the-not-in-clause-in-linq-to-sql.aspx

A quick sample from me:

var orphans = (from c in context.Instances

orderby c.Title

where !(from o in context.CategoryInstances

select o.InstanceID)

.Contains(c.InstanceID)

select c).Skip(PageIndex * PageSize).Take(PageSize);

Essentially, the query does the same thing in C# - that is, to get the list of IDs to check within and then check within it for the ID which is hoping to be not found. Because the whole thing is compiled into SQL before before executed, LINQ generates a NOT EXISTS statement in the WHERE clause, rather than the slower NOT IN.

Concept Car Designs

Found this the other day and thought these were all really cool designs, possibly inspired by the forth-coming Tron movie...

• Interesting gallery of personal designs - http://www.mr-shojaie.com/
• Concept gallery - http://www.carbodydesign.com/gallery/2009/04/30-iran-car-design-exhibition/
• Favourite 1 - http://www.carbodydesign.com/gallery/2009/04/30-iran-car-design-exhibition/14/
• Favourite 2 - http://www.carbodydesign.com/gallery/2009/04/30-iran-car-design-exhibition/16/

Elite For The iPhone And iPad

Unfortunately, I cannot post a link to the game here - I do want to bung down as much as I can and hopefully one day link to it...

I would love to see the Archimedes version of Elite - in my opinion the best version, because it had solid 3D graphics and very smooth controls - ported to the iPhone and iPad, possibly with the iPhone being able to act as a remote control for the iPad running the game.

However, first, a link to nostalgia:

• http://www.iconbar.com/forums/viewthread.php?newsid=879

The company Frontier, started by David Braben which now continues the Elite legacy:

• http://elite.frontier.co.uk/

Ian Bell's Elite FAQ:

• http://www.iancgbell.clara.net/elite/faq.htm

For emulating the Acorn:

• http://arcem.sourceforge.net/

Server Error With Virtual Directory

Trying to put a virtual directory under a web site in WinSrv2003, I hit this problem:

Server Error in '/TestSubSite' Application.

---

Configuration Error

Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Could not load file or assembly 'SControls' or one of its dependencies. The system cannot find the file specified. (D:\web\testsite\web.config line 211)

Source Error:

Line 209: Line 210: Line 211: Line 212: Line 213:

Source File: D:\web\testsite\web.config Line: 211

---

Fortunately, the answer is to wrap the system.web element in a location element, with the attributes path="." and inheritInChildApplications="false".

I've documented this fun on stackoverflow.com:

• http://stackoverflow.com/questions/3297190/iis6-virtual-directory-not-accessible-as-an-app/3297257#3297257

Useful links:

http://forums.asp.net/t/1164283.aspx

http://dotnetslackers.com/Security/re-55457_Stopping_ASP_NET_web_config_inheritance.aspx

http://msdn.microsoft.com/en-us/library/ms178685.aspx