I don t know if it gives exactly what you are looking for, but AppDomain.CurrentDomain.BaseDirectory could be a candidate.

Update
As @AZ pointed out, there are cases when this will not return what you would typically consider the "application directory", so in the end I would say that no, there is no uniform way that will securely give you what you expect.

[Assuming you mean the bin folder] This is how I do it.

If your environment is typically Windows apps and Asp.Net, then you should:

• Check to see if AppDomain.CurrentDomain.SetupInformation.PrivateBinPath is not empty or null.
  • If not, then check to see if it is rooted or not
    • If not, then remember this value as BinPath (it ll be bin in Asp.Net) - but beware that more custom AppDomain hosting environments might have more than one path here and could have a rooted path.

Then, either

• It s AppDomain.CurrentDomain.BaseDirectory
• Or Path.Combine(AppDomain.CurrentDomain.BaseDirectory, BinPath) (where BinPath is remembered from earlier).

There are some other advanced scenarios with this - Test Runners hosting a temporary domain for unit tests, and other strange things. Asp.Net also has it s dynamic folder which has been mentioned elsewhere on this answer - but that s a red-herring if you re just looking to get at the bin folder reliably.

You certainly can t just use the Entry Assembly s path - because in an Asp.Net site that will be dynamically generated and will reside in that dynamic folder.

Equally - there are things like Sql Server-hosted domains to consider, which changes the ballgame again (in this case you d get the MSSQL Server folder).

So any solution that can reliably determine this for any AppDomain is actually going to be best produced by trial and error I m afriad - until somebody comes up with a complete answer for every hosting scenario! So stick with your most common ones.

Assembly.GetExecutingAssembly().Location. It always gets you the path of the executing dll or exe (will be in bin folder for web apps) then you can deduce the app directory from it

I had the same question because I am writing a framework component that runs in unit test assemblies as well as ASP.NET web sites.

I did not test all combinations, but I did test the following code under IIS Express 7.5 and in Visual Studio while running unit tests using the CodeRush plug-in, and it worked fine.

I ll give credit to an old section of the MSDN documentation for putting me on this path: http://msdn.microsoft.com/en-us/library/aa457089.aspx#howtoexecutingapppath_topic3

Anyway, this is the code. Hope it helps:

string binPath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase);
string appPath = binPath.Substring(0, binPath.LastIndexOf("bin", StringComparison.InvariantCultureIgnoreCase));