Start.csを修正する

namespace sqlserver_connection_demo
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        private SqlConnectionStringBuilder stringBuilder = new SqlConnectionStringBuilder()
        {
            InitialCatalog = "DemoDB",
            DataSource = "localhost",
            UserID = "sa",
            Password = "sa"
        };
        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.AddControllers();
        services.AddDbContext<DemoContext>(opt =>
        {
            opt.UseSqlServer(stringBuilder.ToString())
        })
    }
 
    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
 
        app.UseHttpsRedirection();
 
        app.UseRouting();
 
        app.UseAuthorization();
 
        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}