Four 4 tips for developing Windows Services more efficiently

Are you building Windows Services?

I recently did some work with Windows Services, and since it had been rather a long while since I’d done so, I had to recall a couple of tips and tricks from the depths of my memory in order to get my “edit, run, test” cycle to be efficient. The singular challenge for me was quickly getting into a debuggable state with the service. How I did this is described below.

Does Windows Azure support Windows Services?

First, a trivia question…

Trivia Question: Does Windows Azure allow you to deploy your Windows Services as part of your application or cloud-hosted service?

Short Answer: Windows Azure is more than happy to run your Windows Services! While a more native approach is to use a Worker Role, a Windows Service can surely be deployed as well, and there are some very good use cases to recommend them.

More Detailed Answer: One good use case for deploying a Windows Service: you have legacy services and want to use the same binary on-prem and on-azure. Maybe you are doing something fancy with Azure VM Roles. These are valid examples. In general – for something only targetting Azure – a Worker Role will be easier to build and debug. If you are trying to share code across a legacy Windows Service and a shiny new Windows Azure Worker Role, consider following the following good software engineering practice (something you may want to do anyway): factor out the “business logic” into its own class(es) and invoke it with just a few lines of code from either host (or a console app, a Web Service, a unit test (ahem), etc.).

Windows Services != Web Services

Most readers will already understand and realize this, but just to be clear, a Windows Service is not the same as a Web Service. This post is not about Web Services. However, Windows Azure is a full-service platform, so of course has great support for not only Windows Services but also Web Services. Windows Communication Foundation (WCF) is a popular choice for implementing Web Services on Windows Azure, though other libraries work fine too – including in non-.NET languages and platforms like Java.

Now, on to the main topic at hand…

Why is Developing with Windows Services Slower?

Developing with Windows Services is slower than some other types of applications for a couple of reasons:

It is harder to stop in the Debugger from Visual Studio. This is because a Windows Service does not want to be started by Visual Studio, but rather by the Service Control Manager (the “scm” for short – pronounced “the scum”). This is an external program.
Before being started, Windows Services need to be installed.
Before being installed, Windows Services need to be uninstalled (if already installed).

Tip 1: Add Services applet as a shortcut

I find myself using the Services applet frequently to see which Windows Services are running, and to start/stop and other functions. So create a shortcut to it. The name of the Microsoft Management Console snapin is services.msc and you can expect to find it in Windows/System32, such as here: C:\Windows\System32\services.msc

A good use of the Services applet is to find out the Service name of a Windows Service. This is not the same as the Windows Services’s Display name you seen shown in the Name column. For example, see the Windows Time service properties – note that W32Time is the real name of the service:

Tip 2: Use Pre-Build Event in Visual Studio

Visual Studio projects have the ability to run commands for you before and after the regular compilation steps. These are known as Build Events and there are two types: Pre-build events and Post-build events. These Build Events can be accessed from your Project’s properties page, on the Build Events side-tab. Let’s start with the Pre-build event.

Use this event to make sure there are no traces of the Windows Service installed on your computer. Depending on where you install your services from (see Tip 3), you may find that you can’t even recompile your service until you’ve at least stopped it; this smooths out that situation, and goes beyond it to make the usual steps happen faster than you can type.

One way to do this is to write a command file – undeploy-service.cmd – and invoke it as a Pre-build event as follows:

undeploy-service.cmd

You will need to make sure undeploy-service.cmd is in your path, of course, or else you could invoke it with the path, as in c:\tools\undeploy-service.cmd.

The contents of undeploy-service.cmd can be hard-coded to undeploy the service(s) you are building every time, or you can pass parameters to modularize it. Here, I hard-code for simplicity (and since this is the more common case).

set ServiceName=NameOfMyService

net stop %ServiceName%
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\installutil.exe /u %ServiceName%
sc delete %ServiceName%
exit /b 0

Here is what the commands each do:

Set a reusable variable to the name of my service (set ServiceName=NameOfMyService)
Stop it, if it is running (net stop)
Uninstall it (installutil.exe /u)
If the service is still around at this point, ask the SCM to nuke it (sc delete)
Return from this .cmd file with a success status so that Visual Studio won’t think the Pre-Build event ended with an error (exit /b 0 => that’s a zero on the end)

In practice, you should not need all the horsepower in steps 2, 3, and 4 since each of them does what the prior one does, plus more. They are increasingly powerful. I include them all for completeness and your consideration as to which you’d like to use – depending on how “orderly” you’d like to be.

Tip 3: Use Post-Build Event in Visual Studio

Use this event to install the service and start it up right away. We’ll need another command file – deploy-service.cmd – to invoke as a Post-build event as follows:

deploy-service.cmd $(TargetPath)

What is $(TargetPath) you might wonder. This is a Visual Studio build macro which will be expanded to the full path to the executable – e.g., c:\foo\bin\debug\MyService.exe will be passed into deploy-service.cmd as the first parameter. This is helpful so that deploy-service.cmd doesn’t need to know where your executable lives. (Visual Studio build macros may also come in handy in your undeploy script from Tip 2.)

Within deploy-service.cmd you can either copy the service executables to another location, or install the service inline. If you copy the service elsewhere, be sure to copy needed dependencies, including debugging support (*.pdb). Here is what deploy-service.cmd might contain:

set ServiceName=NameOfMyService

set ServiceExe=%1
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\InstallUtil.exe %ServiceExe%

net start %ServiceName%

Here is what the commands each do:

Set a reusable variable to the name of my service (set ServiceName=NameOfMyService)
Set a reusable variable to the path to the executable (passed in via the expanded $(TargetPath) macro)
Install it (installutil.exe)
Start it (net start)

Note that net start will not be necessary if your Windows Service is designed to start automatically upon installation. That is specified through a simple property if you build with the standard .NET template.

Tip 4: Use System.Diagnostics.Debugger in your code

If you follow Tip 2 when you build, you will have no trouble building. If you follow Tip 3, your code will immediately begin executing, ready for debugging. But how to get it into the debugger? You can manually attach it to a running debug session, such as through Visual Studio’s Debug menu with the Attach to Process… option.

I find it is often more productive to drop a directive right into my code, as in the following:

void Foo()
{
int x = 1;
System.Diagnostics.Debugger.Launch(); // use this…
System.Diagnostics.Debugger.Break(); // … or this — but not both
}

System.Diagnostics.Debugger.Launch will launch into a into debugger session once it hits that line of code and System.Diagnostics.Debugger.Break will break on that line. They are both useful, but you only need one of them – you don’t need them both – I only show both here for illustrative purposes. (I have seen problems with .NET 4.0 when using Break, but not sure if .NET 4.0 or Break is the real culpret. Have not experienced any issues with Launch.)

This is the fastest way I know of to get into a debugging mood when developing Windows Services. Hope it helps!