IHostingEnvironment.WebRootPath is null when using EF7 commands

Question

Problem

When I try to add a migration to my code, e.g: dnx ef migrations add initial,

the env.WebRootPath in Startup(IHostingEnvironment env) is null.

This will give me compilation errors when adding a new migration or updating the database.

The Code

In the Startup.cs class I have these lines in the constructor:

public Startup(IHostingEnvironment env)
{
    // ...
    MyStaticClass.Initialize(env.WebRootPath);
    // ...
    _hostingEnvironment = env;
}

Here env.WebRootPath is null and in the Initialize function this throws an exception.

In the ConfigureServices function of the Startup.cs I resolve my class dependencies:

public void ConfigureServices(IServiceCollection services)
{
    // ...
    services.AddInstance<IMyService>(new MyService(_hostingEnvironment.WebRootPath))
    // Note: _hostingEnvironment is set in the Startup constructor.
    // ...
}

Notes

I can build, run, and deploy the code fine. Everything works!
However I made a change in the model and want to add a migration with this command: dnx ef migrations add MyMigration then I see the compilation errors in the package manager console.
I am using ASP 5 web application, and Entity Framework 7

I added wwwroot folder in my application and it worked fine. — user3087175, Jun 24 '19 at 05:27

score 46 · Answer 1 · answered Jun 23 '16 at 09:59

46

The env.WebRootPath can also be null if the wwwroot folder has been inadvertantly removed from the root of your project. Adding a wwwroot folder to the root of your project will also fix this issue.

answered Jun 23 '16 at 09:59

Ricky Keane

1,220
2
12
18

2

Yep. This was it. Thanks for this very simple answer. – James Haug Jun 03 '19 at 12:50

score 17 · Accepted Answer · answered Feb 10 '16 at 19:34

There is an issue reported on github regarding my problem:

https://github.com/aspnet/EntityFramework/issues/4494

I used the workaround in the comments now it seems to be working fine:

if (string.IsNullOrWhiteSpace(_env.WebRootPath))
{
   env.WebRootPath = Path.Combine(Directory.GetCurrentDirectory(), "wwwroot");
}

Paul de Champignon · Answer 3 · 2020-03-14T20:31:16.407

This thread is I believe best one to find out the answer for this problem.

Method 1:

I spent a bit of time looking for answer and I figured out that the way to sort this out rather than check if path exists(in controller or methods) is to update your Program.cs:

    public static async Task Main(string[] args)
    {
        IWebHost webHost = CreateWebHostBuilder(args).Build();

        await webHost.RunAsync();
    }

    private static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseWebRoot("wwwroot")
            .UseStartup<Startup>();

This way you will ensure that there will be webroot folder ready for placing files inside it and _environment.webRootPath will not be null and also you can even customize the name of the folder.

Method 2

The second option to do this is to manually add "wwwroot" folder in the project from Visual Studio level. The program should pick this up and allocate as wwwroot folder:

For me the issue was solved by adding `.UseWebRoot("wwwroot")`. Thanks. — JHBonarius, Jan 01 '21 at 14:39

score 4 · Answer 4 · answered Jun 27 '17 at 12:53

4

In my case, the problem was that the wwwroot folder was empty and VS didn't recognized it.

The solution: create a placeholder.txt in wwwroot.

Hope it helps.

answered Jun 27 '17 at 12:53

Ricardo Smarzaro Igreja

41
2

If wwwroot folder is empty, env.WebRootPath variable is null. – ddagsan Oct 26 '18 at 07:12

score 0 · Answer 5 · edited Feb 07 '19 at 09:02

0

In case someone still faces this problem, in my case the issue was default constructor which I created it for a test.

So, remove the default constructor if any.

edited Feb 07 '19 at 09:02

Ajay2707

5,345
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answered Oct 29 '17 at 19:13

M.Nour Berro

477
4
14

score 0 · Answer 6 · answered Oct 05 '18 at 13:32

I got the error while file uploading in asp.net core application with Telerik controls. The error is not related to Telerik control.

While investigation I got the description that This is the variable which gives the same functionality as Server.MapPath given in asp.net

Good explanation:- What is the equivalent of Server.MapPath in ASP.NET Core?

//this code from above link that how it will be used in the code
public class HomeController : Controller
{
    private readonly IHostingEnvironment _hostingEnvironment;

    public HomeController(IHostingEnvironment hostingEnvironment)
    {
        _hostingEnvironment = hostingEnvironment;
    }

    public ActionResult Index()
    {
        string webRootPath = _hostingEnvironment.WebRootPath;
        string contentRootPath = _hostingEnvironment.ContentRootPath;

        return Content(webRootPath + "\n" + contentRootPath);
    }
}

This is the actual code which gives me the error, I replace the WebRootPath with another way to solve the issue and it works. you can assign and use in the entire application.

public async Task<ActionResult> SaveAsync(IEnumerable<IFormFile> files)
        {
            // The Name of the Upload component is "files"
            if (files != null)
            {
                foreach (var file in files)
                {
                    var fileContent = ContentDispositionHeaderValue.Parse(file.ContentDisposition);

                    // Some browsers send file names with full path.
                    // We are only interested in the file name.
                    var fileName = Path.GetFileName(fileContent.FileName.ToString().Trim('"'));

                    //The below line gives the error
                    //var physicalPath = Path.Combine(HostingEnvironment.WebRootPath, "App_Data", fileName);

                    //and I replace with this (but we can use this variable at multiple location by assign a physical path)
                    var physicalPath = Path.Combine(Path.Combine(Directory.GetCurrentDirectory(), "wwwroot"), "App_Data", fileName);

                    //The files are not actually saved in this demo
                    using (var fileStream = new FileStream(physicalPath, FileMode.Create))
                    {
                        await file.CopyToAsync(fileStream);
                    }
                }
            }

            // Return an empty string to signify success
            return Content("");
        }

ps2goat · Answer 7 · 2018-12-11T23:51:48.837

I was faced with the same issue but with what seems a unique scenario to this post, so I'll add it.

I have a solution with several nested projects. Similar to this:

> Solution
  > MvcProject
    > wwwroot
    > // etc.
  > SecondMvcProject
  > AnotherMvcProject

When running my MvcProject, the IHostingEnvironment had the ContentRootPath set to the Solution folder, and the WebRootPath was null.

Per other people's answers, adding a wwwroot folder in the Solution folder made WebRootPath have a value, but it was the Solution folder path. I had to modify my launch task's current working directory (cwd) in VS Code. It defaulted to "cwd": "${workspaceFolder}", and I had to change it to "cwd": "${workspaceFolder}/MvcProject"

Update

I had this same problem again on another machine, and was glad I commented on this. This time, the problem was that we didn't have any files in one of our wwwroot folders, and empty folders don't get committed to git repos. Add a file to your folder, if you need it!

(It was there for consistency with setup for static file handling. We'll eventually have something in there before the project launches!)

IHostingEnvironment.WebRootPath is null when using EF7 commands

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