System.ArgumentNullException: Value cannot be null. (Parameter 'connectionString')

Question

I add appsettings.json in order to get connection string but I cannot get my connection string. Here is my code.

public class MovieTheaterDBContextFactory : IDesignTimeDbContextFactory<MovieTheaterDBContext>
{
    public MovieTheaterDBContext CreateDbContext(string []Args)
    {
        IConfigurationRoot configuration = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
            .Build();

        var ConnectionString = configuration.GetConnectionString("MovieTheaterDBContext");
        //var ConnectionString = "Server=DESKTOPM4\\SQLEXPRESS;Database=MovieTheaterManagerment;Trusted_Connection=True;";
        var optionsBuilder = new DbContextOptionsBuilder<MovieTheaterDBContext>();
        optionsBuilder.UseSqlServer(ConnectionString);

        return new MovieTheaterDBContext(optionsBuilder.Options);
    }

   
}

appsettings.json:

{
  "ConnectionStrings":
  {
    "MovieTheaterDBContext": "Server=DESKTOPM4\\SQLEXPRESS;Database=EshopSolution;Trusted_Connection=True;"
  }
}

Update: It is my mistake, I have not set this project as startup project.So it can't find appsettings.json.

Answer 1

Right click on appsettings.json file and go to the properties and change "Copy to output directory" option to "Copy always"

Answer 2

Check that your appSettings.json file is in the directory where all your projects file are located. Where the.csproj is located.