Programming

Creating a plugin architecture in a C# application is a fairly easy task. The video below will walk you through the process of setting up the plugin architecture and it will implement a simple plugin.



The source for the project can be downloaded Here.

The video below gives an overview of creating a ComboBox that does conditional formatting. The code uses regular expressions to determine if an item in a combobox should have special formatting. The code is nowhere near production ready, but it should give you an idea of how to do formatting of items in a combobox drop down list. See the full post if you want to copy the code.

If you have used the Visual Studio Extensions for Sharepoint to create more than one list, then you will probably be familiar with the problem of all custom List Definitions are given the name ListDefinition1. This causes problems when you activate the feature, because SharePoint already thinks ListDefinition1 exists.

To fix this problem, there are a few things that need to be changed in your project.

1.) Rename the ListDefinition1 folder in your solution.
2.) Change the URL in the Instance.XML. You'll probably want to change the display name as well, but that is not necessary.
3.) Change the Name in the ListDefinition.xml. Again, you'll probably want to change the display name as well.

Some things to keep in mind are that the display name column is used in one of the folder names that is created by the extensions, so if you use a character that SharePoint doesn't like (i.e. an apostrophe) you will get an error.

If you get an error when deploying, your best bet is to fix the error in VS, delete the PKG folder, and then rebuild and deploy your solution.

A while back I created a little custom panel in VB.Net that supported a gradient background color.



And the results:



This example is not particularly configurable, but it could easily be modified to set the GradientMode and Colors via properties. This would make it into a reusable component.

Getting the current day of week in C# is pretty easy, if all you need is the english version of the day, for example:
But if you want to get the Day of Week for the current language the computer is setup for, the above code will not work. You need to access the Globalization class and get the day of week from there. The snippet of code below, demonstrates how to do it:

I was having this problem at a customer site where we were seeing very poor performance in one of our applications that utilized an API that connected to a SQL database. At first glance I thought there was some memory leak in my code. I went through it line by line and made sure that everything was cleaned up in all circumstances. I found a few places for improvement, ran the code again, and we were still experiencing performance issues.

After a bit more research (and fiddling around), I found that if I restarted SQL server many of my problems went away. I started to think there was an issue with some of the maintenance plans on the database or some processor or RAM setting in SQL server. After checking all of the settings multiple times, I found that everything was set correctly.

On a whim, I decided to run Process Explorer, by Sysinternals, to see if it could tell me more. Well it definitely showed me more. I found that there were handles running wild in the program. There were 3 in particular that kept showing up:

\BaseNamedObjects\{SERVERNAME}MSSQLSERVER_AcceptReady
\BaseNamedObjects\{SERVERNAME}MSSQLSERVER_MUTEX
\BaseNamedObjects\{SERVERNAME}MSSQLSERVER_SERVER_SHARED

This made me focus on SQL server again. I started writing very small test applications and found that the error only occurred when I connected to the database through one particular DSN. I deleted and recreated the DSN and that fixed all of my issues. I wish I had kept the old DSN around, just to see what the exact cause was, but I do have a theory about what happened. The ODBC DSN entries contain pointers to a driver file to use. It is my contention that the faulty DSN was pointing to an old driver (i.e. SQL SP2) which had a known memory leak in it when connections and disconnections were done very frequently.

I have started playing with using Generics in C# and I think they have some great uses. I use ArrayLists in many places in applications to keep track of groups of variables that are all of the same type. The generics will let me explicitly state what is going to be stored in the array, making my code easier to maintain. It also removes the need to cast an item from an Object to it's correct type every time I need to access it.

Here is a small sample of how to use a generic list:

            //Create our List
            System.Collections.Generic.List<House> Houses = new List<House>();

            //Populate the list with Items
            Houses.Add (new House("1234 Main St.","Royal Oak", "MI", "48123"));
            Houses.Add (new House("8825 Fifth Ave.","New York", "NY", "98653"));
            Houses.Add (new House("5456 South Lawn Rd.","Oak Creek", "IN", "65789"));

            //Retreive an item from the list 
            //(Note: there is no need to cast this, because it is already of type House)
            House x = Houses[2];

            //You can still loop through the items in the generic lists
            foreach (House oHouse in Houses)
            {
                listBox1.Items.Add(oHouse.Address);
            }

So I am trying to download the release version of the .Net Framework version 2.0 when it tells me that it needs Microsoft Windows Installer 3.0 to continue. I go to try and download that and they tell me that I need Windows Genuine Authentication. I try to do the authentication process and I ran into a myriad of issues.

1.) It detects that I am using an alternate browser (Firefox) and says that active-x controls cannot be run. It then allows me to download an HTA file to run on my machine to do the authentication. I try to do that and there is a script error in the HTA file.

At this point, I decided that I should try IE.

2.) I go through the same process and because I have IE set to not download Active-X controls, it takes me to the same HTA file and this time it just gives me a "Page cannot be displayed" error.

3.) I go to the WGA (Windows Genuine Authentication) help page and it points me to a link if I am having issues with the WGA process. I click the link and it tries to take me to a page on the Microsoft communities area, but the page does not work and it just leaves my browser blank.

I decided to suck it up and let the active-x controls run in my still rather locked down IE and it still would not work. I am thinking that it has something to do with some scripting that I don't allow.

I finally got it working by adding Microsoft as a trusted site (ughh), running the WGA process and then removing microsoft from my trusted sites.

If Microsoft is going to require that you have WGA to download some of their products, then they should make sure that it works on all browsers and have clear (and technical) instructions on how to get it working.

So I have started on the XM interface for the classes that I have written previously. My main focus was making it work and I will worry about the looks of the application later. I have it connecting to XM and playing the streaming media via Windows media player. I am making some nice progress, but I really want to make the channel list screen look nice, so I will probably work on that next.

So I have started tinkering around with the idea of making my own application to listen to XM radio streams from the internet. Once you dissect the calls they make to the server it is actually not that hard. There are essentially 3 calls that talk to their server to set all of the information that is needed to get your media player a valid streaming URL:

1.) Login info

http://xmro.xmradio.com/xstream/login_servlet.jsp?user_id=username&pword=password

Now calling this first URL sets a session cookie, so keep that cookie around, so you can do #2 and #3.

2.) Get the channel list

http://player.xmradio.com/padData/pad_data_servlet.jsp?all_channels=true
- or -
http://player.xmradio.com/padData/pad_data_servlet.jsp?channel=150


The first URL gets the complete list of channels, while the second gets the information for channel 150 only.

3.) Get a media stream URL

http://player.xmradio.com/player/2ft/playMedia.jsp?ch=150&speed=high

This url returns to us an XML string, that we can then parse to get out the filename to send to our media player.