Tip To Log

We often like to know what happens in a procedure and also we like to figure out if we see something in the log, where in the code it happened. Therefore it is handy to start and end each procedure with log. To do this we can put a small generic code like this


Trace.WriteLine("Beginning with " + System.Reflection.MethodInfo.GetCurrentMethod().Name);

it will work just fine

Linq-To-SQL and WCF

WCF works on the objects like disconnected records. The object that is passed to the client is not the same as the one the is about to update. Therefore Linq does not know about the changes made to the record. As a result Linq will not do anything when calling the SubmitChanges.

To sort out this problem we need attach the instance record again to the list in the context:

context.GetTable().Attach(instance, true);

just before we call the SubmitChanges. But this is not always possible. I got the following error when calling this:

An entity can only be attached as modified without original state if it declares a version member or does not have an update check policy.

The simple way of sorting this out was giving the ID field of the record the attribute of

IsVersion=true

This way Linq allows me to attach the existing instance and generate an UPDATE sql-statement.


See Also: http://www.west-wind.com/Weblog/posts/135659.aspx

Using Linq-To-SQL classes as DataContract in WCF

Coming accross a nice tutorial from Jesse Liberty

He describes the trick to get the Link-To-SQL data classes generated to be consumed as DataContract. In his document he points out that you need to set the Serialization Mode property of the dbml surface to Unidirectional.

Common Buses and their Max Bandwidth

Nice article from: http://networking.ringofsaturn.com/PC/pciexpress.php

Bandwidth
PCI Express in all it's flavors: 1x, 2x, 4x, 8x, 16x and 32x all have much greater bandwidth than basic PCI.

Common Buses and their Max Bandwidth
PCI 132 MB/s
AGP 8X 2,100 MB/s
PCI Express 1x 250 [500]* MB/s
PCI Express 2x 500 [1000]* MB/s
PCI Express 4x 1000 [2000]* MB/s
PCI Express 8x 2000 [4000]* MB/s
PCI Express 16x 4000 [8000]* MB/s
PCI Express 32x 8000 [16000]* MB/s
IDE (ATA100) 100 MB/s
IDE (ATA133) 133 MB/s
SATA 150 MB/s
Gigabit Ethernet 125 MB/s
IEEE1394B [Firewire] 100 MB/s

using UriTemplate

Copied from MSDN:

The UriTemplateTable class provides a mechanism for managing a collection of UriTemplate objects. This makes it easy to call Match on the table to find all templates that match the supplied Uri. Alternatively, you can call MatchSingle to ensure it matches only a single UriTemplate in the table.

Uri baseUri = new Uri("http://contoso.com/bookmarkservice");
UriTemplate uriTemplate = new UriTemplate( "users/{username}/bookmarks/{id}");

// generate a new bookmark URI
Uri newBookmarkUri = uriTemplate.BindByPosition(baseUri, "skonnard", "123");

// match an existing bookmark URI
UriTemplateMatch match = uriTemplate.Match(baseUri, newBookmarkUri);
System.Diagnostics.Debug.Assert(match != null);
Console.WriteLine(match.BoundVariables["username"]);
Console.WriteLine(match.BoundVariables["id"]);


Catch the Session Expired case

The project I am working on requires to show a nice custom error page to the user when the session is expired. I searched a bit on the internet and came up with a good solution in forums.asp.net which I worked it out as follows:

As mentioned in the forum you need to implement an IHttpModule and redirect the context'e AcquireRequestState event to your method which goes this:

        void Application_AcquireRequestState(object sender, EventArgs e)
      {
          if (HttpContext.Current.Session != null && HttpContext.Current.Session.IsNewSession)
          {
              if (HttpContext.Current.Request.Cookies != null && HttpContext.Current.Request.Cookies["ASP.NET_SessionId"] != null)
              {
                  HttpContext.Current.Session.Clear();
                  HttpContext.Current.Response.Redirect("/Errors/SessionTimeout.aspx", true);
              }
          }
      }
    
  }

As you can see I clear the session before redirecting to the SessionTimeout.aspx. The reason for that is that I want the user have a choice of going to login screen by providing a link in the SessionTimeout.aspx. And the login requires a session state unlike the SessionTimeout.aspx that has the attribute EnableSessionState="False" 

URL properties of Request to ASP.NET

The following attributes are some of the usefull properties of the URL object. I use the following url to send my request to localhost:


http://localhost/Test/Asghar.aspx?test=fine


And I get the following results:

AbsolutePath = /Test/Asghar.aspx
AbsoluteUri = http://localhost/Test/Asghar.aspx?test=fine
Authority = localhost
DnsSafeHost = localhost
Fragment =
Host = localhost
HostNameType= Dns
IsAbsoluteUri = True
IsFile = False
LocalPath = /Test/Asghar.aspx
OriginalString = http://localhost:80/Test/Asghar.aspx?test=fine
PathAndQuery = /Test/Asghar.aspx?test=fine
Port = 80
Query = ?test=fine
Scheme = http
UserEscaped = False
UserInfo =

And the code to do it is as followes:

    AbsolutePath = <%= System.Web.HttpContext.Current.Request.Url.AbsolutePath %><br />
     AbsoluteUri = <%= System.Web.HttpContext.Current.Request.Url.AbsoluteUri %><br />
     Authority = <%= System.Web.HttpContext.Current.Request.Url.Authority %><br />
     DnsSafeHost = <%= System.Web.HttpContext.Current.Request.Url.DnsSafeHost %><br />
     Fragment = <%= System.Web.HttpContext.Current.Request.Url.Fragment %><br />
     Host = <%= System.Web.HttpContext.Current.Request.Url.Host %><br />
     HostNameType= <%= System.Web.HttpContext.Current.Request.Url.HostNameType.ToString() %><br />
     IsAbsoluteUri = <%= System.Web.HttpContext.Current.Request.Url.IsAbsoluteUri %><br />
     IsFile = <%= System.Web.HttpContext.Current.Request.Url.IsFile %><br />
     LocalPath = <%= System.Web.HttpContext.Current.Request.Url.LocalPath %><br />
     OriginalString  = <%= System.Web.HttpContext.Current.Request.Url.OriginalString  %><br />
     PathAndQuery = <%= System.Web.HttpContext.Current.Request.Url.PathAndQuery %><br />
     Port = <%= System.Web.HttpContext.Current.Request.Url.Port %><br />
     Query = <%= System.Web.HttpContext.Current.Request.Url.Query %><br />
     Scheme = <%= System.Web.HttpContext.Current.Request.Url.Scheme %><br />
     UserEscaped = <%= System.Web.HttpContext.Current.Request.Url.UserEscaped %><br />
     UserInfo = <%= System.Web.HttpContext.Current.Request.Url.UserInfo %><br />
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