More than one DbContext was found

Question

I am implementing a code first database using AspCore 2. I have a "DataContext.cs" that goes like this:

public class ApplicationUser : IdentityUser
{
    public string FirstName { get; set; }
    public string MiddelName { get; set; }
    public string LastName { get; set; }
    public bool IsActive { get; set; }
    public DateTime? DateAdded { get; set; }
}

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

protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
             base.OnModelCreating(modelBuilder);

          //AspNetUsers -> User
        modelBuilder.Entity<ApplicationUser>()
            .ToTable("User");
        //AspNetRoles -> Role
        modelBuilder.Entity<IdentityRole>()
            .ToTable("Role");
        //AspNetUserRoles -> UserRole
        modelBuilder.Entity<IdentityUserRole>()
            .ToTable("UserRole");
        //AspNetUserClaims -> UserClaim
        modelBuilder.Entity<IdentityUserClaim>()
            .ToTable("UserClaim");
        //AspNetUserLogins -> UserLogin
        modelBuilder.Entity<IdentityUserLogin>()
            .ToTable("UserLogin");
    }
}

and this in my "startup.cs"

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<DataContext>(x => x.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseMvc();
    }
}

When I try running the dotnet migration, dotnet ef migrations add InitialCreate I get the following error:

"More than one DbContext was found. Specify which one to use. Use the '-Context' parameter for PowerShell commands and the '--context' parameter for dotnet commands."

How can this be resolved?

Answer 1

It looks like there are several classes that have been inherited from DbContext class (may have come from some NuGet package). So add migration with

Add-Migration MyMigration -context DataContextName