Tahir Hassan's Blog

emacs init.el

2011-09-12T15:01:00.001-07:00

Emacs - Setting up C-z for Undo

2011-09-12T06:34:00.001-07:00

Type M-x, global-key-set , C-z (the new key combination), undo.

If you want it to be a little more permanant, put this in .emacs/init.el:

Common Text Operations in Emacs

2011-08-25T14:11:00.001-07:00

Deleting text

The two 'pure' deletion methods are using backspace or delete keys. The other way is to cut the text using the below method, regardless of the fact that it copies it to the clipboard.

Cut, Copy and Paste

To cut text, we first need to set a 'mark'. This is the start of the region of text that will be cut. We then need to move the cursor to the end of the region and type C-w.

To copy text, we do exactly the same as we do for cutting, except we use M-w instead of C-w.

To paste text we use C-y.

Installing Emacs On Windows 7

2011-08-24T14:34:00.001-07:00

To install emacs...

First download it from the official site:
http://ftp.gnu.org/pub/gnu/emacs/windows/
The one I downloaded was emacs-23.3-bin-i386.zip but download the latest version.
Within the zip file, I found a folder called emacs-23.3 which is replete with folders such as bin, etc and info etc. Copy emacs-23.3 to C:\Program Files\.
Now create a folder in C:\Users\<My Name>\AppData\Roaming called .emacs.d, within it we want to create a file called init.el. This is the file that emacs reads when it loads up.

Add the following lines to init.el (Be sure to replace <My Name>):
Now it would be a good idea to make a shortcut to C:\Program Files\emacs-23.3\bin\runemacs.exe.
EDIT: later when I tried using the application is came up with a curious error message:
Error (initialization): User has no home directory
Due to this, I created a laucher batch script containing the following text:

This batch script sets up the HOME to be that Roaming directory wherein we created the .emacs.d folder.

You have finished installing the application!

Getting Column Names From SQL Server

2011-07-20T08:59:00.000-07:00

To retrieve information about columns of a table in SQL Server you need to excecute the sp_columns stored procedure (example is using Project table):

Running this sp gives you more information than you want. You are only interested in the COLUMN_NAME column in the result. To get only COLUMN_NAME you need to use OPENROWSET as below:

The only inelegant aspect of this solution is that we are passing as an argument, the same connection string which we used to connect to the database server in the first place, to OPENROWSET.

Another method, which does not require OPENROWSET is as follows:

Current State of Modeless Editing (Version Control)

2011-05-16T02:48:00.000-07:00

This is the change control of the ModelessEditing.ahk file.

The most recent is at the top, so it is in descending order.

XXXXXXXXXXXXXXXXXXXXXXXXXXX

Debugging MVC App under IIS

2011-02-03T09:26:00.001-08:00

Sometimes you need to debug an application but because of certain techniques, you MUST host your application under IIS rather than using the in-built Visual Studio web server.

Once you create your virtual directory under IIS you need to create a Wildcard mapping to point to (for .NET version 4): For anything other than .NET version 4: And then untick Check that file exists.

Next you need to make sure that Integrated Windows authentication is enabled through the Directory Security tab.

JQuery Context Menu

2010-11-03T04:14:00.000-07:00

I have had a look at many JQuery context menu plugins and all of them are incredibly inflexible. For example jQuery.contextMenu can only be used for right clicks only, and can only show an unordered list as opposed to any html.

What I have found is that JQuery UI's Dialog is sufficient to create any arbitrary context menu as all we need to do is bind to the "contextmenu" event and show a dialog. Secondly JQuery UI Dialog will handle all the sizing and positioning (although you need to provide it with the viewport x and y coordinates).

Below is a little plugin that I have devised which defines two JQuery functions; one called setUpContextMenu which essentially creates a JQuery UI Dialog and keeps it closed by using { autoOpen: false } option. The second function called openContextMenu will display the context menu and will close the dialog if the user clicks outside the context menu:

All in all, only 34 lines of code.

Let's go through an example. Imagine that you have a context menu div that contains four or so options which we will represent as links:

Firstly we want to turn the links above into block elements and secondly turn them into JQuery UI Buttons:

Next we want to turn the context-menu div into a context menu on page load: Thirdly we want to bind the contextmenu event of the document to show the context-menu div, so that it shows whenever the body is right clicked: Thus when you right click you will see the following:

Rendering Json in MVC

2010-10-03T12:00:00.001-07:00

To render Json into an MVC view, you will need to use System.Web.Script.Serialization.JavaScriptSerializer which MVC uses internally when you call JsonResult.

Ideally what we would like to do is render a JSON object onto the page and then be able to refer to it through our script. For this we must attach it to the window object:
Then in our views we can then render a specific object that was passed to it from the controller: Then in our Javascript, we can then refer to the object using the window[object-name] property:

XmlSerializer Helper class

2010-07-06T14:00:00.000-07:00

A lot of the times, you will want to use C# in built XML (de-)serialization facilities in the exact same way: You begin with a object which you want to serialize and then you serialize it and then put the resulting string into the database, or alternatively you want to take an existing serialized object and deserialize to perform further actions with it.

The following class is a wrapper written specifically for this purpose. The contructor takes one or more type arguments (all of which may been to be serialized by this serializer) and then provides essentially two methods, one for serializing and one for deserializing. Additional overloads have been written for XElement because I am using LINQ To SQL which uses the XElement class to represent an XML column.

NullsLast Extension method for Property Name

2010-06-16T03:32:00.000-07:00

Continuing on from my previous post regarding sorting a column by putting the nulls at the end rather than at the beginning, I have found a need to write a NullsLast extension method that takes a string which represents the property's name instead of an expression which represents the property. This was needed for use with MvcContrib's Html Grid for which one can use the OrderBy extension method found in MvcContrib.Sorting namespace. The way that you would want to use the extension method would be to specify the name of the property as a string: It turns out that this method's definition is very similar to the definition of earlier NullsLast Definition with the exception that we need to use reflection to get the PropertyInfo using the property name string parameter. We then proceed as usual to construct a equals expression using the property and the null constant and then call OrderBy with the newly constructed (x => x.property == null) expression:

MVC Html Grid Sorting by Composite Column

2010-06-16T03:18:00.000-07:00

Sometimes when using MvcContrib's Grid feature you may end up with columns which are a composite of two or more properties or you might have formatting in the expression. For example, you may have the following: For such expressions, although the content generated is correct, it does not include a "Column" parameter on the column header link to sort the column. For the above example, we would naturally want to sort by the Name rather than the Description. It would be useful to have an extension method on IGridColumn which could be called as follows: The above extension method was quite easy to write but since the author has made the GridColumn.Name property with only a get accessor and no set, I had to use reflection in order to retrieve the underlying field and then set it:

MVC: SelectListFor extension method bug for Indexed Values

2010-06-14T13:13:00.000-07:00

At my current company I am using the MVC Framework. Although it is fairly mature, (I am using version 2), there are still loads of little bugs. One such bug is the SelectListFor extension method which when given an indexed or indexer value, for example:

it will generate the correct html but the selected value of the drop down list is ignored on the first GET request. On a POST request, since we receive a form value of the name "Tasks[0].Name", the extension method will then fill in the correct selected value since it can look this up. However we are interested in solving the problem for the initial GET request.

One problem I had with developing a solution was the fact that in the MVC source, everything is either internal or private, therefore I cannot reuse the MVC code, and instead I have to copy and paste huge chunks of it into my own application. Another major drawback of this is that if there are any bug fixes within MVC, then my application will not benefit from them.

Anyhow, the following class solves the problem. The extension method is called "SelectListFor2" which is understandable because we do not want a naming conflict between our own extension method and Mvc's built in one:

You would then use it by adding the relevant namespace into your web.config file and then using it as: (Notice the 2).

Linq to Sql: Order By Nulls Last

2010-06-02T15:12:00.000-07:00

In SQL Server if you use "ORDER BY", you will get null values first. However this is not the intention of the end user who wants to see items with values in those columns.

Especially in LINQ to SQL, there is no extension method where we can easily do this. The only way is a cumbersome

Which gets cumbersome after a point, especially when you forget to do it and then have to hunt for the code which does the ordering.

The solution is surprisingly simple. We want to be able to call it as:

I have defined two extension methods which do so, one called NullsLast which makes sure that those objects with null values will appear last, and the other OrderByNullsLast which orders the collection and which puts the null values at the end:

Deletion Auditing Trigger in SQL Server

2010-05-13T09:40:00.000-07:00

To audit deletions of rows in a SQL Server database, you can use a trigger to log the xml of the table row to a deleted rows table:

Linq Exception: The null value cannot be assigned to a member with type System.Guid which is a non-nullable value type.

2010-05-04T06:27:00.000-07:00

This exception is caused by having a non-nullable field on an object but the database having a nullable field of the same name.

For example, I had a class defined in the dbml called Resource which had a System.Guid field called TeamId but on the SQL Server, the Resource.TeamId field in fact allowed null values

Configuring an MVC Web App under IIS 6

2010-04-23T07:48:00.000-07:00

To configure an MVC web application under IIS 6 you first need to create a virtual directory. During the Virtual Directory Creation Wizard you can leave the Access Permission as it is (merely leave Read and Run Scripts ticked and ignore the other options).

You must then change the options of the virtual directory. Right click it and go into Properties. On the Virtual Directory tab, click on the Configuration button.

On the next screen, click Add. For the executable, set it to point to:

Set the extension to .* and untick Check that file exists.

Using MvcContrib's Html Grid and Pager

2010-04-22T04:28:00.000-07:00

To use MvcContrib's Html Grid and Pager you need to include references to both Microsoft.Web.Mvc.dll and MvcContrib.dll which are included in MvcContrib. In your aspx file you need to include the following namespaces:

For hyperlinks you will want to include a statement to DoNotEncode on the column:

To apply attributes on the td tag of a particular column then you can do so with a call to Attributes extension method:

Occasionally you need access to the underlying object when deciding on the style of a table cell. For example, you may want to highlight all unread items with the color red:

As you can see above, you can access the rows object by using row.Item.

You can find more information from David Hayden's blog and Jerry Skinner's blog.

Swapping Mouse Buttons with AutoHotKey

2010-04-15T14:14:00.000-07:00

To prevent repetitive strain injury, you may want to change the hand that you control your mouse with, frequently, like every hour or so. Therefore you will want a quick method of swapping the left and right mouse buttons because changing the mouse options from the Control Panel takes too long.

An additional requirement could be that you want the mouse buttons to be swapped natively without mouse click interception. The benefit of this would be that your mouse clicks are much faster and more reliable and this matters when playing games.

The only way of swapping mouse buttons without any overhead is to use the Win32 function SwapMouseButton:

Adding Files and Folders / Directories to Google Sites

2010-03-23T14:07:00.001-07:00

Although Google sites may not support FTP access and you certainly cannot upload files or folders to your Google site in the traditional way, you can have the appearance of having added files and folders.

To add a folder you first have to click "Create Page":

Then we specify to create a file cabinet, then we give the name of the folder, and then specify which folder we want it under. For the example below I have it under the root (sites.google.com/site/tahassan/) so that the folder location would be sites.google.com/site/tahassan/folder1.

To add a file under this folder1 we click on "Add File":

Then adding a file is a very easy process.

Let's say we wanted to add a folder under folder1, called "folder2"? This is a very easy process. We would click on "Create Page" (like in the first picture), then we would click on "Choose a different location", then we can specify the location to be folder1:

Although this is not perfect, you can still use it to organise files into folders.

Setting up Alex Gorbatchev's Syntax Highlighter on Blogger

2010-03-21T10:24:00.000-07:00

Because my blog posts are essentially technical notes, I found a need to include code samples, especially in C#. Currently, the syntax highlighter most in vogue is Alex Gorbatchev's Syntax Highlighter. Here is an example of what it is capable of:

I had a bit of trouble setting it all up as I have no real website to host the Syntax Highlighter source files. Since I am a cheapskate, I ended up using Google Sites. Be aware though, that Google Sites is slow so your blog may take longer to load. If you do not want to go through the bother of uploading the source files you can instead use the files I have uploaded instead (as I describe below).

Below are steps that you would need to follow in order to set it up on Blogger.

1. Download the Syntax Highlighter source files and upload them to a location on the web. I am assuming that you have uploaded it to SITE/syntaxhighlighter where SITE is your website address. Inside the syntaxhighlighter folder you should have three sub-folders: scripts, styles and src. (I am using Syntax Highlighter 2.1.364).

If you do not wish to upload the files yourself you can instead replace SITE with in what follows.

2. In Blogger, click on Settings -> Formatting and set "Convert Line Breaks" option to No.

3. In Blogger, click on Layout -> Edit HTML. Here you want to add the following under the <head> element: (Replace SITE with the address of your actual site.)

4. To write a code sample you merely have to write:

Extracting info From SqlException when attempted Deletion causes a Reference Violation

2010-03-21T05:12:00.000-07:00

When you try to delete a row using LINQ to SQL using code similar to the following: a SqlException can be thrown if this object has any child rows associated with it.

I have written code below, which, given a SqlException, first tests whether it was thrown due to a reference constraint violation, and finds out the contraint name, the name of the table that the child row exists in, and the name of the column that acts as the foreign key:

Re-Syncing subtitles with Subtitle Workshop

2010-03-02T10:22:00.000-08:00

If you have a movie where the subtitle file that you downloaded is not in sync, then don't worry: there is an easy process to re synchronise them using a free program called "Subtitle Workshop". Subtitle Workshop can be downloaded here.

To resync, follow the instructions below:

1) Open Subtitle Workshop (the link can be found in "Start" -> "All Programs" -> "URUSoft" -> "Subtitle Workshop").

2) Open the video file by using ("Movie" -> "Open") and also open the the subtitle file by using "File" -> "Load Subtitle".

3) Play the movie (the play button is the left most button below) and pause it immediately when the speech begins.

You can find the length of the video already played by looking at the right of the above bar (the top value).

4) You then note down when the first subtitle was played. You can find this out by looking at the "Show" column in the table below the movie (look at the first row):

5) Assuming that the subtitles are shown before the speech started then work out:

6) Once you have done this arithmetic, you can then use ("Edit" -> "Timings" -> "Set Delay") and then input this calculated offset and then hit ("File" -> "Save"). Note that a back up of the subtitle file should be made before doing this. This is the end of the process.

If on the other hand, the subtitles are shown before the speech starts then we work out the offset by:

Then we follow the same process to set the delay except that it should be minus (-):

Setting up an ASP .NET Web Application Project Under IIS for the First Time

2010-02-28T03:27:00.000-08:00

Once you have created your website, you will want to deploy it. To deploy it as a web application under IIS (Internet Information Services) do the following:

1. First install IIS if you already haven't done so. Go to Start -> Settings -> Control Panel -> Add or Remove Programs -> Add/Remove Windows Components and then check Internet Information Services and click Next to install.

2. Secondly, if you already haven't done so, open a command prompt (to do this go to Start -> Run and then type "cmd" and press enter. Now type "aspnet_regiis.exe -i". This will register the ASP .NET runtime as the executable for ASP .NET applications.

3. Now go into IIS (Start -> Control Panel -> Adminitrative Tools -> Internet Information Services) and then in the left column expand the items (press the + button) until you see "Default Web Site". Right click this and then select "new -> Virtual Directory". Type in a meaningful website name here when it prompts for the alias. When prompted for the directory, browse to folder containing the web application project. This folder should contain the project file, the web.config and the bin directory. For the access permissions make sure that the first three items are checked (Read, Run and Execute).

4. Now right click the folder containing the web application project in Windows explorer and select properties. Go to the Security Tab. You will need to add the ASPNET account to this list as well as an account named IUSR_MACHINE where MACHINE is the name of your machine. If you dod not know your computer name, right click on the My Computer Icon on your desktop and then select properties. Go to the "Computer Name" tab. For both ASPNET and IUSR_MACHINE set the permissions to allow "Read, "Read & Execute" and "List Folder Contents".

ASUS M4A78-VM and Realtek sound

2009-10-15T16:22:00.000-07:00

I bought the ASUS M4A78-VM and tried to install Windows XP (32-bit) on it. Every driver on the CD worked, except the sound driver.

I searched Google for ages, but I figured it out in the end. The way you go about it is as follows:

Firstly remove existing HD Audio Drivers and the Realtek drivers: go to Start -> Control Panel -> Add / Remove Programs and uninstall the Realtek High Definition Audio Driver. Secondly remove any High Definition Audio Drivers that are listed under "Sound, video and game controllers" in the Device Manager. Open this by doing Start -> Run -> type "devmgmt.msc" and enter.

Go into the Device Manager. You should see two "PCI Devices" with question marks on them. Right click them and select "Update / Install Drivers" (or something to that effect). This will "install" them. Do this for both of the devices with the question marks.

Lastly insert the motherboard CD and install the audio drivers.