How do you resolve a virtual path to a file under an OWIN host?

问题

Under ASP.NET and IIS, if I have a virtual path in the form "~/content", I can resolve this to a physical location using the MapPath method:

HttpContext.Server.MapPath("~/content");

How can you resolve a virtual paths to a physical location under an OWIN host?

回答1:

You may use AppDomain.CurrentDomain.SetupInformation.ApplicationBase to get root of your application. With the root path, you can implement "MapPath" for Owin.

I do not know another way yet. (The ApplicationBase property is also used by Microsoft.Owin.FileSystems.PhysicalFileSystem.)

回答2:

You shouldn't use HttpContext.Server as it's only available for MVC. HostingEnvironment.MapPath() is the way to go. However, it's not available for self-hosting owin. So, you should get it directly.

var path = HostingEnvironment.MapPath("~/content");
if (path == null)
{
    var uriPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().GetName().CodeBase);
    path = new Uri(uriPath).LocalPath + "/content";
}

回答3:

I'm adding another answer that would work for ASP.NET Core. There is a service IHostingEnvironment, and it's added by the framework.

public class ValuesController : Controller
{
    private IHostingEnvironment _env;

    public ValuesController(IHostingEnvironment env)
    {
        _env = env;
    }

    public IActionResult Get()
    {
        var webRoot = _env.WebRootPath;
        var file = Path.Combine(webRoot, "test.txt");
        File.WriteAllText(file, "Hello World!");
        return OK();
    }
}

回答4:

I have an API running on OWIN self-host (no System.Web) - ran into this issue needing to load a text file where we maintain a list.

This worked for me, found from a co-worker - config.text is right in my root next to web.config:

var path = AppDomain.CurrentDomain.BaseDirectory + "/config.txt";

回答5:

You may have few different implementations of function like

Func<string, string>

provided by different startup code under key like

"Host.Virtualization.MapPath"

and put it into OWIN dictionary. Or you can create basic class like this

public abstract class VirtualPathResolver { 
    string MapPath(string virtualPath);
}

and pick implementation either by configuration setting, command line parameter or environment variable.

回答6:

The Accepted answer, AppDomain.CurrentDomain.SetupInformation.ApplicationBase, did not work for me under dnx / kestrel - it returned the location of the .dnx runtime and not my webapp route.

This is what worked for me inside OWIN startup:

public void Configure(IApplicationBuilder app)
        {
        app.Use(async (ctx, next) =>
            {
                var hostingEnvironment = app.ApplicationServices.GetService<IHostingEnvironment>();
                var realPath = hostingEnvironment.WebRootPath + ctx.Request.Path.Value;

                // so something with the file here

                await next();
            });

            // more owin setup
        }

来源：https://stackoverflow.com/questions/24571258/how-do-you-resolve-a-virtual-path-to-a-file-under-an-owin-host

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