Events vs Delegates in C#

Today, somebody asked me to explain the difference between an event and a delegate in C#. Despite using the language for a long time now, I was quite taken back by the fact that couldn't describe the exact difference. The only thing I knew was that one need to define a delegate to declare an event.

A bit of searching took me to this very well explained post on the subject http://blog.monstuff.com/archives/000040.html

To sum it all up, an Event is actually a modifier on delegate i.e. makes it more restrictive. The main differences are

1) Event can be used in an interface definition while a delegate cannot be used.

2) Event can only be invoked from the class that declares it, while delegates can be invoked from child classes and clients.

3) Event comes with it's pair of accessors i.e Add and Remove. An event is always assigned and unassigned with a += and -= operator.

4) Event has a restrictive signature and must always be of the form Event (object source, EventArgs args)

Well, you learn something new everyday...

RegForm Tool and Visual Studio

If you have used Microsoft InfoPath to create electronic forms, you would no doubt be familiar with the Regform tool. The tools is a command line utility that allows you to

• Automatically make a backup copy of the form template
• Make the necessary changes to the .xsf file and XML template file to make the form fully trusted
• Update the version number of the form template
• Package the files in the .xsn CAB file format
• Create a custom installation program for installing the fully trusted form

Now, the RegForm uses Microsoft Visual Studio 2005 (Visual Studio 8) to create the installer and won't work if you have Visual Studio 2008 or Visual Studio 2010 installed on your machine. Well, there is a heck around it. The following registry setting contains the path to the latest version of visual studio installed on your machine

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\devenv.exe

If you change the setting from "%ProgramFiles%\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe" or "%ProgramFiles%\Microsoft Visual Studio 10.0\Common7\IDE\devenv.exe" to "%ProgramFiles%\Microsoft Visual Studio 8\Common7\IDE\devenv.exe", assuming you have visual studio 2005 installed on your machine, the RegForm tool would work correctly.

Missing Reference name while building with Team Build

I recently spent quite a lot of time, uncovering this rather bizarre looking error in our Team Build. We start getting it when I moved one happy perfectly working build from a TSF 2008 build agent running to a new TFS 2010 Build agent. As soon as I ran the build on the new server, I start getting an error in one of the projects

Class1(14,27): error CS0234: The type or namespace name 'Class1' does not exist in the namespace 'namespace1' (are you missing an assembly reference?)

Tried the same build in the original Build agent and it did built without any problems. Ran the build again with diagnostics log. From the log files I spotted that where my project was getting compiled using Csc.exe , it didn’t include reference to a project. So, I checked again where the project being reference was getting built and yes it was. Also, it was built before the project what was referencing it. So on the face of it everything looked good. But it won’t still build!

Next thing was to try building the solution manually using MSBUILD. So wrote something like

Msbuild.exe mysolution.sln

It ran successfully without a hitch. Now, it was getting interesting. But hang on Team Build does use Multi-processor support while invoking msbuild. So, ran msbuild again with a /m switch

Msbuild.exe /m mysolution.sln

Here we go, I got exactly the same problem. So the build work fines when someone is compiling using one processor but not with multi-processor. So, what happened there?

With some support from Microsoft Visual Studio support team, found that it could be a problem that that path of the project file was too long. So looked back and yes it was. The path of the project that the other project was referencing was 262 characters. Reduced the path length by reconfiguring my build agent to build on a shorter named base directory and bang it worked correctly.

So, if you hit by this problem that a build doesn’t work when maxcpucount is greater than one, do check your path lengths.

TF215097: An error occured while initializing a build

Since, I spent a significant amount of time resolving this issue while moving our team project and builds from TFS 2008 to TFS 2010, I thought to write it down in my blog so that anyone stuck in the same quagmire might find some help.

We have been looking to leverage some exciting new features in TFS 2010 and team build in our project so when the RTM release was issued last Monday we decided to make the move instantly.

The migration process is simple, straight forward and well-documented. I must give it to Microsoft who has done tremendous work to make the whole installation process much simpler and a far cry from early days of TFS 2005.

Once installed, I followed the configuration wizard to upgrade my projects, which went pretty smoothly as well. The last block in the puzzle was to make Team build to work. So, I disabled the build service of TFS 2008 and installed TFS 2010 build service on our build machines. The wizard picked up existing build agents and created a Build Controller and Build agent for me. Ran the build and bang it all worked.

I ran the built again and got the following error

TF215097: An error occured while initializing a build for build definition \Gateway2.0\2.7_Gateway. There was no endpoint listening at http://ggtfs26build1.9191/Build/v3.0/Services/Controller/21 that could accept the message. This is often caused by an incorrect address or SOAP action. See InnerException, if present, for more details.

Confused as to why it worked the first time around and not second time, I looked in to the properties of the build controller where it failed. Clicked the Test Connection button and it worked correctly. Tried the build again and got the same error. Finally, after restarting my build agents and build controllers and my TFS collections I was able to do a build again only for it to fail again.

After talking to a few people in the Microsoft Visual Studio team, got to know that there are two methods TestConnection and StartBuild. While the TestConnection method always succeeded the StartBuild would fail. After running some traces on my TFS server, they found that the calls to StartBuild, which goes directly through w3wp.exe succeed but if they are called via TFSJobAgent, it won’t succeed, and since the call to TestConnection always go through w3wp.exe, it always succeeded.


The innerException on my build machine suggested that the proxy could not be resolved. So, I changed my internet connection settings, restarted my TFSJobAgent service and ran a build. Again, the build ran fine the first time around but failed in the second go. Though, it did not resolve the issue but helped to identify that the exception is coming in from the Job Agent service.

The next step was to enable tracing in TFSJobAgent service. You can do that by going to the C:\Program Files\Microsoft Team Foundation Server 2010\Application Tier\TFSJobAgent directory and add the following within the listeners tag in <System.Diagnostics> section

<add name="myListener" type="System.Diagnostics.TextWriterTraceListener" initializeData="C:\logs\jobagent.log" />

Also, change the value from 0 to 4 in each of the switches. My System.Diagnostics section looked like this

<system.diagnostics>

<trace autoflush="false" indentsize="4">

<!--To enable tracing to file, simply uncomment listeners section and set trace switch(es) below.
Directory specified for TextWriterTraceListener output must exist, and job agent service account must have write permissions. -->

<listeners>

<add name="myListener"
type="System.Diagnostics.TextWriterTraceListener"
initializeData="C:\logs\jobagent.log" />

<remove name="Default" />

</listeners>

</trace>

<switches>

<!-- Trace Switches
Each of the trace switches should be set to a value between 0 and 4, inclusive.
0: No trace output
1-4: Increasing levels of trace output; see Systems.Diagnostics.TraceLevel-->

<add name="API" value="4" />

<add name="Authentication" value="4" />

<add name="Authorization" value="4" />

<add name="Database" value="4" />

<add name="General" value="4" />

<add name="traceLevel" value="4" />

</switches>

</system.diagnostics>

Restarted the service and check the entries in the job agent. After a few minutes, the following error appeared in the log file

[Error, PID 3916, TID 6784, 13:29:49.002] Exception: {
Exception Message: Team Foundation services are not available from server http://:8080/VSTSCI/WebServices/notifyservices.asmx?proj=7fd3fa6a-33bb-4ec8-8cfd-9e6a9cc59015.
Technical information (for administrator):
Unable to connect to the remote server (type TeamFoundationServiceUnavailableException)

Exception Stack Trace: at Microsoft.TeamFoundation.Client.TeamFoundationClientProxyBase.CreateSoapRequest(String methodName, HttpWebRequest& request, XmlWriter& requestXml)
at Microsoft.TeamFoundation.JobService.Extensions.Core.TeamFoundationNotificationClient.Notify(String eventXml, String tfsIdentityXml, Subscription subscription)
at Microsoft.TeamFoundation.JobService.Extensions.Core.NotificationJobExtension.SendSoapNotification(TeamFoundationRequestContext requestContext, TeamFoundationNotification notification, TeamFoundationIdentityService identityService)

Inner Exception Details:

Exception Message: Unable to connect to the remote server (type WebException)
Exception Stack Trace: at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
at System.Net.HttpWebRequest.GetRequestStream()
at Microsoft.TeamFoundation.Client.TeamFoundationClientProxyBase.CreateSoapRequest(String methodName, HttpWebRequest& request, XmlWriter& requestXml)

Inner Exception Details:

Exception Message: No connection could be made because the target machine actively refused it OldTFSIPAddress:8080 (type SocketException)

Exception Stack Trace: at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)


This was rather strange that i could see web services calls made to my old TFS server, which had been upgraded. So, I did a repair of TFS installation and hurrah the builds start running merrily.

Now, I don’t know if it is an upgrade issue or anything peculiar in our team project which might have caused this error but hopefully with this post you would have an idea on how to resolve this issue. So, if you spot this issue

1) Make sure that the build servers and controller could speak to each other. If the TestConnection button is working, it is a good indication that there is no comms error.

2) Make sure that your proxy settings are correct on TFS server for the user under who’s context the TFS Build Agent is running.

3) If the error still exists, enable tracing on TFSBuildAgent service and see if it is logging an errors.
Apart from the above error, I also got the behaviour that the build would start but the build service could not find the build agent. Internally, it doesn’t start the build either.

No option to connect to Analysis Services in Microsoft Management Studio

I spent about an hour on this issue today so thought to jot it down here to save someone else's time.

I had a new installation of Microsoft SQL Server 2008 and tried to connect to Analaysis Service using Microsoft SQL Server Management Studio. But the only options I could see in the drop down list in the "Connect to Server" dialog were "Database Engine" and "SQL Server Compact Engine".
Verified that "Analysis Services" and were running and whether the port was allowed in Windows Firewall but everything seemed to be fine.

Then I decided to repair my installation to see if I have missed out on any feature and yes that was certainly the case. From the features option, there is an option to install "Management Tools - Basic" and there is an option to install "Management Tools - Complete". I had it installed with Management Tools Basic and that is why I couldn't see all the options.

Authentication error while communicating with web server

I started debugging one of our sites today after having a new 64 bit virtual machine with Windows 2003 Server installed on it. After setting up all websites, code, etc and when I pressed F5 on my Visual Studio 2008, I got the following error

"Unable to start debugging on the web server. An authentication error occurred while communicating with the web server"

Most of the answers on net point to doing an IISRESET and enabling HTTP Keep-alives, neither of which worked for me. But the following link proved to be useful and after carrying out the steps, it finally start working for me.

http://support.microsoft.com/?id=896861

Blogging it, as it might be useful for somebody else.