Overview

Startup.cs

public class Startup
{
    // Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        //... ... ...
    }

    // Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app)
    {
        //... ... ...
    }
}

ConfigureServices

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

    public void ConfigureServices(IServiceCollection services)
    {

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

        services.AddDefaultIdentity<IdentityUser>(options => options.SignIn.RequireConfirmedAccount = true).AddEntityFrameworkStores<ApplicationDbContext>();

        services.AddRazorPages();
		
        //... ... ...
    }
	
    public void Configure(IApplicationBuilder app)
    {
        //... ... ...
    }
}

Configure

public class Startup
{

    public void ConfigureServices(IServiceCollection services)
    {
        //... ... ...
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Error");
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapRazorPages();
        });
    }
}

Multiple Startup

See: