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What is the recommended way of allowing an ASP.NET application to know which environment it runs in? My application can run in these environments:

  • Debugging within Visual Studio
  • An automated system test
  • Deployment on a staging server
  • Deployment on a production server

In each of these environments the application needs some different configuration. The main difference between the environments is which database connection settings to use, but there are also other differences.

This is what I have tried:

  • I have tried using the "configuration" option in Visual Studio. By default there is two: Release and Debug. I have tried to replace these two with identifiers for my four environments. These configurations can then be used to apply a transform to the Web.config file. The problem here is that choosing the configuration happens on build time, and I would like to compile my application and then choose the environment before running it on a web server. The Web.config transformation also doesn't happen when debugging inside Visual Studio, so instead of telling the application that it runs in the debugging environment, it gets no environment. I found a workaround at Use Visual Studio web.config transform for debugging but it doesn't seem to work well. I have to change the configuration in the project properties, which is a slow process.
  • I have tried using an environment variable. This way I could set a variable MYAPP_ENV=dev from outside the application, and I could read it in C# as
    string env = System.Environment.GetEnvironmentVariable("MYAPP_ENV");
    But then I am not sure how to set this environment variable from within Visual Studio and from within IIS. I cannot set it globally on the machine because the same machine needs to be able to run the application in multiple environments.

So, how is the recommended way of doing this in ASP.NET? In Ruby on Rails I would use the RAILS_ENV environment variable, and in PHP I would include a file, which is not checked into the repository and is added to the ignore list of the version control system.

Community
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Jesper Kristensen
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  • It's not clear if you are doing this but I would try to refrain from using writing environment specific code (i.e. `if env=="dev" { } else { }` because then your site behaves differently in different environments. Any values that need to be changed should be changed in config files (see AaronS answer). – Jeff Jan 05 '12 at 15:15

2 Answers2

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I would have separate web.config files for each of your environments.

Alternatively, You could also have something set up similar to what you did with your PHP include file by adding an external config file.

Just add the following to your web.config.

<appSettings file="MySettings.config">

Then add a new file called MySettings.config that contains the rest of your config information.

AaronS
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    +1. To help maintain separate web.configs I recommend taking advantage of [config transforms](http://msdn.microsoft.com/en-us/library/dd465318.aspx) in Visual Studio. – Keith Jan 05 '12 at 15:15
  • AronS: This sounds interesting. How do I set up Visual Studio to automatically put one value into the MySettings.config file before running my application when I start debugging (F5)? And would this MySettings.config file be available next to the dll with my application when I deploy it on IIS in production? Keith: As I originally wrote, it looks like the transform can only be made as part of the build process, and there are other complications which seems to make it not work effectively. – Jesper Kristensen Jan 06 '12 at 13:18
  • What you would do is similar to how you set up your PHP version. Just have this file in each of your environments, and have your deploy tool ignore it. What I actually do is have multiple versions of my web.config in a sub-folder, renamed for each environment (web.config.QA, web.config.Prod, etc). My build and deploy process then selects the correct one, based on which build is being performed, renames it to web.config, and then replaces the one in the root as the site is being deployed. This has worked really well for me. – AaronS Jan 06 '12 at 15:12
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The web.config file is used for environmental configurations. If you find configuration in visual studios to be too cumbersome you can just keep the file out of version control, and edit it for each environment. in the <appSettings> node you can add keys:

<appSettings>
    <add key="Environment" value="DEV" />   
</appSettings>

Then you can access these values via the ConfigurationManager class

var currentEnvironment = ConfigurationManager.AppSettings["Environment"].ToString();
Jeff Lauder
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  • It would not make much sense to have the entire web.config outside of version control or to have one version of it for each environment, since there are a lot of stuff, which has to be in the file, but is not really environment or configuration related. – Jesper Kristensen Jan 06 '12 at 13:23