Null Blazor 托管的 ConfigureServices 中的 WebRootPath

Question

I would like to access the web root path from within Blazor.Server.Startup.ConfigureServices in a Blazor Hosted solution.

I have injected IWebHostEnvironment into the Startup constructor and saved it as a property called "WebHostEnvironment". The problem is that in ConfigureServices, WebHostEnvironment.WebRootPath is always null.

I have already verified that:

• wwwroot folder exists in my Blazor.Client project.
• app.UseStaticFiles(); has been called in Startup.Configure (not sure if this is necessary, but it is one of the few recommended solutions I've found).

This seems to be a common problem (perhaps WebRootPath is only populated under certain conditions - such as after my app is published/deployed?), however I've been unable to find a clear, definitive answer anywhere and I'm not sure what I can do to obtain the web root path in ConfigureServices .

Use Case

While not directly relevant to the question, I'm trying to obtain the path to my token endpoint so that that I can configure the TokenUrl property in a new OpenApiAuthFlow for Swashbuckle's AddSwaggerGen service. I'd prefer not to have to specify the localhost URL since this will eventually be deployed to a production website. I suppose I could store it in appsettings if needed, but I had hoped not to have to maintain the path there.

services.AddSwaggerGen(options =>
    {
        options.SwaggerDoc("v1", new OpenApiInfo {Title = "Protected API", Version = "v1"});
        options.AddSecurityDefinition("oauth2", new OpenApiSecurityScheme
        {
            Type = SecuritySchemeType.OAuth2,
            Flows = new OpenApiOAuthFlows
            {
                AuthorizationCode = new OpenApiOAuthFlow
                {
                    AuthorizationUrl = new Uri("https://localhost:5000/connect/authorize"),
                    TokenUrl = new Uri("https://localhost:5000/connect/token"),
                    Scopes = new Dictionary<string, string>
                    {
                        {"api1", "Demo API - full access"}
                    }
                }
            }
        });
    });

Answer 1

It's not a bug but a feature; you just cannot do what you want in ConfigureServices .
If you want to access to the wwwroot folder put your code in Configure method or in a method of ServiceCollection you can get a IServiceProvider instance such as .AddTransient .

sample

services.AddTransient(p =>
{
    var environment = p.GetRequiredService<IWebHostEnvironment>();
    var path = environment.WebRootPath;
    return new Stuff(path);
});

Answer 2

Try adding a "wwwroot" folder to your Blazor server project (assuming you have the standard 3 projects in your solution - client, server, and shared). The folder itself can be empty, but it needs to be there, otherwise the WebRootPath will be null.