'No suitable constructor found for entity type string
Yesterday I came her with a similar question about my own made entity type that head some errors. I fixed up these errors but now it throws one on entity type string and I have absolutely no clue how to fix this.
Full exception:
System.InvalidOperationException: 'No suitable constructor found for entity type 'string'. The following parameters could not be bound to properties of the entity: 'value', 'value', 'startIndex', 'length', 'value', 'value', 'startIndex', 'length', 'value', 'value', 'startIndex', 'length', 'value', 'startIndex', 'length', 'enc', 'c', 'count', 'value'.'
This gets thrown when I launch my application: I've written a data seeder to get some data in my database. I've scoped this class in my ConfigureServices and used it in the Configure method.
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();
}
And in this class gets the error thrown:
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
but this isn't the only time this exeception gets thrown, it also gets thrown when I try to load a certain page of my application:
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());
}
}
Every time I try to load the view connected to this Index in this controller, the same exepcetion gets thrown right here:
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();
}
}
(the interface this class implements:)
public interface IRatingRepository {
IEnumerable<Rating> GetAll();
void Add(Rating rating);
void Remove(Rating rating);
void SaveChanges();
}
I think it has something to do with my rating class:
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
}
but I woudln't know what to do to fix this. Any help would be appreciated!
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());
}
}
RatingConfiguartion
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);
}
}
Solution 1:[1]
The problem is in your context, you have this line:
public DbSet<string> Codes { get; set; }
You need to use a concrete class for your entities, a string cannot be used.
Solution 2:[2]
Just had a similar problem.
I had a class and was doing some changes and deleted the default class constructor. All though it is never called EF still needs it or you will get a No suitable constructor found exception
public class Company
{
public Company ( )
{
// ef needs this constructor even though it is never called by
// my code in the application. EF needs it to set up the contexts
// Failure to have it will result in a
// No suitable constructor found for entity type 'Company'. exception
}
public Company ( string _companyName , ......)
{
// some code
}
}
Solution 3:[3]
This is the same issue I got while adding a new property in my entity and updated the existing constructor and passed new property as a parameter
Fix: Instead of updating an existing constructor, added an overloaded constructor with a new property and this error was gone while creating migration
Solution 4:[4]
This has been answered partially, but there is a general guideline in EF Core that ought to be stated with regard to this problem.
When you defined an Entity in an Entity class, you need to ensure that the entire thing is public and accessable. For example,
public class GroupMap
{
[Key] public int Id { get; set; }
public string GroupId { get; set; }
}
There are two properties, Id (which has a redundant [Key] annotation) and GroupId. Just thinking about GroupId, it must be a public property, and it must have both its getter and setter defined.
So this will fail:
public class GroupMap
{
[Key] public int Id { get; set; }
private string GroupId { get; set; } // private property not allowed
}
As will this:
public class GroupMap
{
[Key] public int Id { get; set; }
public string GroupId { get; } // setter must be defined
}
Since EF Core is ORM, you also need to make sure that the property type makes sense with regard to the database (though I can't provide much detail here). Finally, as stated elsewhere, you also need to provide the correct context definition. All the same rules apply.
For example:
public DbSet<Item> Items { get; set; } // public, and getter & setter defined
As also stated elsewhere, the DbSet type needs to be a concrete class that defines the various properties you wish to be either columns in your table, or relations to another table.
Hope that helps someone out there.
Solution 5:[5]
In my case, this error got resolved after I corrected casing for my fields/properties being mapped.
I'd suggest using:
-Camel case for fields
-Pascal case for properties. Even if your property name is like 'DBProperty', change it to 'DbProperty'
Solution 6:[6]
@DavidG and @BrownPony are correct but I would like to add some more information:
It is not possible to add a default in the constructor like public Company (string companyName = "") but you can use a private constructor.
public class Company
{
private Company ( )
{
}
public Company (string companyName)
{
// some code
}
}
Solution 7:[7]
I ran into this same issue when adding new property to an entity model, and then setting that property in the constructor. Verify that the casing pattern of the constructor matches that of the property.
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
| Solution | Source |
|---|---|
| Solution 1 | DavidG |
| Solution 2 | BrownPony |
| Solution 3 | Raza Ashfaq Mirza |
| Solution 4 | PaulG |
| Solution 5 | zed101 |
| Solution 6 | Ogglas |
| Solution 7 | SeanDykes |