【发布时间】：2022-04-15 21:57:46
【问题描述】：
昨天我向她提出了一个关于我自己制作的实体类型的类似问题，该类型导致了一些错误。我修复了这些错误，但现在它在实体类型字符串上抛出一个错误，我完全不知道如何解决这个问题。
完全例外：
System.InvalidOperationException: '没有为实体类型'字符串'找到合适的构造函数。以下参数无法绑定到实体的属性：'value'、'value'、'startIndex'、'length'、'value'、'value'、'startIndex'、'length'、'value'、' value'、'startIndex'、'length'、'value'、'startIndex'、'length'、'enc'、'c'、'count'、'value'。
当我启动我的应用程序时会抛出这个问题：我编写了一个数据播种器来在我的数据库中获取一些数据。我在ConfigureServices 中定义了这个类，并在Configure 方法中使用了它。
public void ConfigureServices(IServiceCollection services) {
services.Configure<CookiePolicyOptions>(options => {
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(
Configuration.GetConnectionString("DefaultConnection")));
services.AddScoped<IRatingRepository, RatingRepository>();
services.AddScoped<IReservationRepository, ReservationRepository>();
services.AddScoped<DataSeeder>();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env,DataSeeder seeder) {
if (env.IsDevelopment()) {
app.UseDeveloperExceptionPage();
app.UseDatabaseErrorPage();
} else {
app.UseExceptionHandler("/Error");
app.UseHsts();
}
app.UseStatusCodePages();
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseDefaultFiles();
app.UseCookiePolicy();
app.UseMvc(routes => {
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}"
);
});
seeder.SeedData();
}
并且在这个类中得到了抛出的错误：
public class DataSeeder {
#region Fields
private readonly ApplicationDbContext _context;
private Random random;
private ISet<string> _set;
#endregion
#region Constructor
public DataSeeder(ApplicationDbContext context) {
_context = context;
random = new Random();
_set = new HashSet<string>();
}
#endregion
#region Methods
public void SeedData() {
_context.Database.EnsureDeleted();
if (_context.Database.EnsureCreated()) { //**on this line**
AddCodes();
//reservations
Reservation r1 = new Reservation(new DateTime(2019, 2, 21), "Robbe van de Vyver", "Kip met rijst en currysaus", true, "");
_context.Reservations.Add(r1);
_context.SaveChanges();
}
}
private void AddCodes() {
if (_context.Codes.Count() <= 5) {
char[] characters = "azertyuiopqsdfghjklmwxcvbn,;:=?+-./+~ù%^$*&éè!çà|@#0123456789AZERTYUIOPQSDFGHJKLMWXCVBN".ToArray();
for (int i = 0; i < 25; i++) {
string code = "";
for (int j = 0; j < 4; i++) {
code += characters[random.Next(0, characters.Length)];
}
_set.Add(code);
}
_context.Codes.AddRange(_set);
_context.SaveChanges();
}
}
#endregion
但这不是唯一一次引发此异常，当我尝试加载应用程序的某个页面时也会引发此异常：
public class ChezMoutController : Controller {
private IRatingRepository _ratingRepository;
private IReservationRepository _reservationRepository;
public ChezMoutController(IRatingRepository ratingRepository, IReservationRepository reservationRepository) {
_ratingRepository = ratingRepository;
_reservationRepository = reservationRepository;
}
public IActionResult Index() {
ViewData["foodAverage"] = _ratingRepository.GetAll().Select(r => r.FoodRating).Average();
ViewData["atmosphereAverage"] = _ratingRepository.GetAll().Select(r => r.AtmosphereRating).Average();
ViewData["reservations"] = _reservationRepository.GetAll();
ViewData["DatesLeft"] = new List<DateTime>() { };
return View(_ratingRepository.GetAll());
}
}
每次我尝试在此控制器中加载连接到此索引的视图时，都会在此处抛出相同的异常：
public class RatingRepository : IRatingRepository {
private readonly ApplicationDbContext _context;
public RatingRepository(ApplicationDbContext context) {
_context = context;
}
public void Add(Rating rating) {
var any = _context.Ratings.Any(r => r.RatingId == rating.RatingId);
if (!any) {
_context.Add(rating);
}
}
public IEnumerable<Rating> GetAll() {
return _context.Ratings.ToList(); //**on this line**
}
public void Remove(Rating rating) {
var any = _context.Ratings.Any(r => r.RatingId == rating.RatingId);
if (any) {
_context.Remove(rating);
}
}
public void SaveChanges() {
_context.SaveChanges();
}
}
（这个类实现的接口：）
public interface IRatingRepository {
IEnumerable<Rating> GetAll();
void Add(Rating rating);
void Remove(Rating rating);
void SaveChanges();
}
我认为这与我的评分等级有关：
public class Rating {
#region Fields
private double _foodRating;
private double _atmosphereRating;
#endregion
#region Properties
public int RatingId { get; set; }
public double FoodRating {
get {
return _foodRating;
}
private set {
if (value < 0.0 || value > 5.0) {
throw new ArgumentException("Give a score between 0 and 5 please.");
}
_foodRating = value;
}
}
public double AtmosphereRating {
get {
return _atmosphereRating;
}
private set {
if (value < 0.0 || value > 5.0) {
throw new ArgumentException("Give a score between 0 and 5 please.");
}
_atmosphereRating = value;
}
}
public string PersonalMessage { get; set; } //not mandatory
public string Suggestions { get; set; } //not mandatory
#endregion
#region Constructors
public Rating() {
}
public Rating(double foodRating, double atmosphereRating, string personalMessage = null, string suggestions = null):this() {
FoodRating = foodRating;
AtmosphereRating = atmosphereRating;
PersonalMessage = personalMessage;
Suggestions = suggestions;
}
#endregion
}
但我不知道该怎么做才能解决这个问题。 任何帮助将不胜感激！
ApplicationDbContext：
public class ApplicationDbContext : DbContext {
public DbSet<Rating> Ratings { get; set; }
public DbSet<Reservation> Reservations { get; set; }
public DbSet<string> Codes { get; set; }
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options) { }
protected override void OnModelCreating(ModelBuilder modelBuilder) {
modelBuilder.ApplyConfiguration(new RatingConfiguration());
modelBuilder.ApplyConfiguration(new ReservationConfiguration());
}
}
评级配置
public class RatingConfiguration : IEntityTypeConfiguration<Rating> {
public void Configure(EntityTypeBuilder<Rating> builder) {
builder.ToTable("Rating");
builder.HasKey(r => r.RatingId);
builder.Property(r => r.PersonalMessage)
.HasMaxLength(250)
.IsRequired(false);
builder.Property(r => r.Suggestions)
.HasMaxLength(250)
.IsRequired(false);
}
}
【问题讨论】：