设置DBContext时出现ASP.NET Core 2.2错误（在Kestrel中起作用，不在IIS Express中起作用）

Question

I have a .Net Core 2.2 web project where I set up the dbcontext connections in the Startup.cs file:

services.AddDbContext<FirmDirectoryContext>(options =>  
              options.UseSqlServer(Configuration.GetConnectionString("DefaultDatabase")));

When I run this is Kestrel it works, but if I try to run it using IIS Express I get the following:

{System.ArgumentNullException: Value cannot be null. Parameter name: connectionString

The connection string is obviously set in the appsettings.json file, or Kestrel would fail as well?

Answer 1

I'm not sure how your appsettings.json looks like, but you should have a section in your json file like this :

"ConnectionStrings": {
    "DefaultDatabase": "<Your connection string>"
}

Answer 2

If your environment is set as development, dotnet gets connection string from appsettings.development.json.

Make sure you have set connection string there as well.

Answer 3

Looks like the problem was in my Program.cs file. I had copied some code I used from a .NET Core 2.1 project

WebHost.CreateDefaultBuilder(args)
     .UseContentRoot(Directory.GetCurrentDirectory())
     .UseWebRoot(Directory.GetCurrentDirectory() + "\\wwwroot") // THIS LINE FIXES STATIC FILES ON PROD
     .UseIISIntegration()
     .UseStartup<Startup>();

Once I edited it to remove the Directory.GetCurrentDirectory() code it works.

WebHost.CreateDefaultBuilder(args)
     .UseIISIntegration()
     .UseStartup<Startup>();

Now I'll have to test on the server to see if it still works. Thanks for the responses.