.NET Hosting IStartup isn't supported

This is my current Program class:

using System.Net;
using System.Text;
using DatingApp.API.Data;
using DatingApp.API.Helpers;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.AspNetCore.Diagnostics;
using Microsoft.EntityFrameworkCore;
using Microsoft.IdentityModel.Tokens;

namespace DatingApp.API
{
    class Program
    {
        public static void Main(string[] args)
        {

            var builder = WebApplication.CreateBuilder(args);

            // Add services to the container.

            builder.Services.AddControllers();
            // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
            builder.Services.AddEndpointsApiExplorer();
            builder.Services.AddSwaggerGen();

            builder.Services.AddDbContext<DataContext>(options =>
            {
                options.UseSqlServer("DefaultConnection");
            });

            builder.Services.AddCors(x => x.AddPolicy("corsapp", builder =>
                {
                    builder.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader();
                }));

            builder.Services.AddScoped<IAuthRepository, AuthRepository>();
            builder.Services.AddScoped<IDatingRepository, DatingRepository>();

            builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
                .AddJwtBearer(options =>
                {
                    options.TokenValidationParameters = new TokenValidationParameters
                    {
                        ValidateIssuerSigningKey = true,
                        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8
                        .GetBytes(builder.Configuration.GetSection("AppSettings:Token").Value)),
                        ValidateIssuer = false,
                        ValidateAudience = false
                    };
                });

            var app = builder.Build();

            var host = CreateWebHostBuilder(args).Build();
            using (var scope = host.Services.CreateScope())
            {
                var services = scope.ServiceProvider;
                try
                {
                    var context = services.GetRequiredService<DataContext>();
                    context.Database.Migrate();
                    Seed.SeedUsers(context);
                }
                catch (Exception ex)
                {
                    var logger = services.GetRequiredService<ILogger<Program>>();
                    logger.LogError(ex, "An error occurred in migration");
                }
            }



            // Configure the HTTP request pipeline. 
            if (app.Environment.IsDevelopment())
            {
                app.UseSwagger();
                app.UseSwaggerUI();
            }
            else
            {
                app.UseExceptionHandler(builder =>
                {
                    builder.Run(async context =>
                    {
                        context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
                        var error = context.Features.Get<IExceptionHandlerFeature>();
                        if (error != null)
                        {
                            context.Response.addApplicationError(error.Error.Message);
                            await context.Response.WriteAsync(error.Error.Message);
                        }
                    });
                });
            }

            // app.UseHttpsRedirection();

            app.UseRouting();

            app.UseCors("corsapp");

            app.UseAuthentication();

            app.UseAuthorization();

            app.MapControllers();

            app.Run();

            host.Run();

        }

    public static IHostBuilder CreateWebHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<StartupBase>();
                });
    }
}

Here is the error:

>Unhandled exception. System.NotSupportedException: Microsoft.AspNetCore.Hosting.IStartup isn't supported
at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.UseStartup(Type startupType, HostBuilderContext context, IServiceCollection services, Object instance)
at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass14_0.<UseStartup>b__0(HostBuilderContext context, IServiceCollection services)
at Microsoft.Extensions.Hosting.HostBuilder.InitializeServiceProvider()
at Microsoft.Extensions.Hosting.HostBuilder.Build()
at DatingApp.API.Program.Main(String[] args) in D:\Demo\DatingApp\datingapp.api\Program.cs:line 54

It is supposed to run and migrate the data to the database but it didn't run

There is no need to create host and use startup, just create scope from the app.Services:

using(var scope = app.Services.CreateScope())
{
var dbContext = scope.ServiceProvider.GetRequiredService<DataContext>();
// use context
}

As for IStartup - check also this answer.