Not able to configure connection string in ASP.net MVC Core 5.0 & Entity Framework Core application

Question

I'm getting below error when I configure SQL Connection in ASP.Net Core MVC 5 and Entity Framework core.

I've configured in Startup.cs file:

public void ConfigureServices(IServiceCollection services)
{
services.AddControllersWithViews();

        services.AddDbContext<VMSDBContext>(
           options => options.UseSqlServer(Configuration.GetConnectionString("VMSDatabase"))
        );
    } 

My appsettings.json file:

{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"ConnectionStrings": {
"VMSDatabase": "Server=.;Database=VMS;Trusted_Connection=True;"
},
"AllowedHosts": "*"
}
InvalidOperationException: No database provider has been configured for this DbContext. A provider can be configured by overriding the 'DbContext.OnConfiguring' method or by using 'AddDbContext' on the application service provider. If 'AddDbContext' is used, then also ensure that your DbContext type accepts a DbContextOptions object in its constructor and passes it to the base constructor for DbContext.

Answer 1

Your design has a parameterless constructor. You get the error "InvalidOperationException: No database provider has been configured for this DbContext." if you call the parameterless constructor in an Action or Razor Page.

 _context = new VMSDBContext();

Remove the parameterless constructor and always use standard constructor injection which has the following pattern.

    public class IndexModel : PageModel
    {
        private readonly SchoolContext _context;

        public IndexModel(SchoolContext context)
        {
            _context = context;
        }
    }

Answer 2

Hi anonymous user,

Can you post the related code about the VMSDBContext?

From the error message, the issue might relate that your DbContext(VMSDBContext) needs a constructor which accepts a DbContextOptions. You can refer the following sample code which works well on my side:

public class ApplicationDbContext : IdentityDbContext  
{  
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)  
        : base(options)  
    {  
    }  
}  

Appsettings.json

{  
  "ConnectionStrings": {  
    "DefaultConnection": "...connection string..."  
  },  

Code in the ConfigureService method:

        services.AddDbContext<ApplicationDbContext>(options =>  
            options.UseSqlServer(  
                Configuration.GetConnectionString("DefaultConnection")));   

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Best regards,
Dillion