public class ApplicationDbContext : DbContext
{

    // constructor(must)
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
    {
    }

    // table
    public DbSet<ToDo> ToDos { get; set; }
}

string connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
builder.Services.AddDbContext<ApplicationDbContext>(options =>
    options.UseMySql(connectionString, ServerVersion.AutoDetect(connectionString)));