WebApi - How to include relative paths for included App_Data XML files?

Question

Question Background:

I have a WebApi controller who's logic code relies on reading data contained in a number of XML files. These XML files have been included in the App_Data folder of the WebApi project.

The Issue:

I'm trying to use the relative path of the XML files in the following way:

    [System.Web.Http.HttpGet]
    public string CallerOne()
    {
        string docOne = @"~\AppData\DocOne.xml";

        string poll = @"~\AppData\Poll.xml";

        var response =  _Caller.CallService(docOne, poll);

        return ConvertXmlToJson(response);
    }

When running the WebApi code and calling the Url to the CallerOne method I receive the following error:

An exception of type 'System.IO.DirectoryNotFoundException'
occurred in  System.Xml.dll but was not handled in user code

Additional information: Could not find a part of the path
'C:\Program Files  (x86)\IIS Express\~\AppData\FPS.xml'.

I also want to eventually publish this to Azure and include these files.

How can I use the relative path to read in the XML files in the App_Data folder?

Answer 1

Ended up finding the answer.

The following is needed to read the relative paths in a WebApi project:

var fullPath = System.Web.Hosting.HostingEnvironment.MapPath(@"~/App_Data/yourXmlFile.xml");

Answer 2

As jdweng inferred several months back, Environment.GetEnvironmentVariable("AppData") would seem to be the preferred method. The OP's auto-accepted answer and that give quite different results. For example, using both of those in my project, I get:

C:\\Projects\\PlatypusReports\\PlatypusReports\\App_Data\\yourXmlFile.xml

...for the OP's long-winded code, namely this:

var fullPath = System.Web.Hosting.HostingEnvironment.MapPath(@"~/App_Data/yourXmlFile.xml");

...and this:

C:\\Users\\cshannon\\AppData\\Roaming

...for jdweng's code, to wit:

string appData = Environment.GetEnvironmentVariable("AppData");

OTOH, this code:

string appDataFolder = HttpContext.Current.Server.MapPath("~/App_Data/");

returns:

C:\\Projects\\PlatypusReports\\PlatypusReports\App_Data\

So it's very similar in results (if not methodology) to the first example above. I actually got it from a question I asked almost two years ago, which I had forgotten about.

I'm not positive if jdweng's approach would work as expected once the app is deployed on a server, but I have much more confidence in it than the other approaches.

Can anyone verify?

UPDATE

The accepted answer here has 237 upvotes at time of typing, so seems pretty reliable, albeit 6 years old (42 in dog years, which may be a good sign).

Answer 3

Your approach is fine. You just had some tpying error, You wrote

string docOne = @"~\AppData\DocOne.xml";

But it should have been

string docOne = @"~\App_Data\DocOne.xml";