EntityType has no key defined error

Question

Controller   using System  using System Collections Generic  using System Linq  using System Web  using System Web Mvc  using MvcApplication1 Models  using System ComponentModel DataAnnotations Schema   namespace MvcApplication1 Controllers       public class studentsController   Controller                             GET   students           public ActionResult details                         int id   16              studentContext std   new studentContext               student first   std details Single m   gt  m RollNo    id               return View first                        DbContext Model   using System  using System Collections Generic  using System Linq  using System Web  using System Data Entity   namespace MvcApplication1 Models       public class studentContext   DbContext               public DbSet lt student gt  details   get  set              Model   using System  using System Collections Generic  using System Linq  using System Web  using System ComponentModel DataAnnotations Schema   namespace MvcApplication1 Models        Table  studentdetails        public class student               public int RollNo          public string Name          public string Stream          public string Div            Database table   CREATE TABLE  dbo   studentdetails        RollNo   int  NULL       Name   nvarchar  50  NULL       Stream   nvarchar  50  NULL       Div   nvarchar  50  NULL       In global asax cs  Database SetInitializer lt MvcApplication1 Models studentContext gt  null     The above code lists all the classes I am working on  Upon running my application am receiving the error       One or more validation errors were detected during model generation  along with  Entity type has no key defined

User · Answer

You don t have to use key attribute all the time  Make sure the mapping file properly addressed the key  this HasKey t   gt  t Key   this ToTable  PacketHistory    this Property p   gt  p Key               HasColumnName  PacketHistorySK      and don t forget to add the mapping in the Repository s OnModelCreating  modelBuilder Configurations Add new PacketHistoryMap

User · Answer

All is right but in my case i have two class like this  namespace WebAPI Model      public class ProductsModel             Table  products            public class Products                        Key              public int slno   get  set                 public int productId   get  set                public string ProductName   get  set                 public int Price   get  set                        After deleting the upper class it works fine for me

User · Answer

Additionally Remember  Don t forget to add public keyword like this   Key   int RoleId   get  set      wrong method   you must use Public keyword like this   Key   public int RoleId   get  set      correct method

User · Answer

In my case  I was getting the error when creating an  MVC 5 Controller with view  using Entity Framework    I just needed to Build the project after creating the Model class and didn t need to use the  Key  annotation

User · Answer

The object must contain a field which will be used as the Primary Key  if you have a field named Id then this will by default be the primary key of the object to which Entity Framework will link to    Otherwise  you should add the  Key  attribute above that field you wanna use as the Primary Key  and you ll also need to add the namespace System ComponentModel DataAnnotations   public class myClass       public int Id   get  set         Key      public string Name   get  set        https   stackoverflow com a 51180941 7003760

User · Answer

For me  the model was fine  It was because I had 2 different versions of entity framework  One version for the web project and another one for the common project which contains the models   I just had to consolidate the nuget packages     Enjoy

User · Answer

I too solved this issue in my own project by solving this particular line in my code  I added the following   DatabaseGenerated DatabaseGeneratedOption None    After realizing my mistake I then went and changed it to  DatabaseGenerated DatabaseGeneratedOption Identity    This further ensures that the field named  quot Id quot  increments in value each time a new row is inserted in the database

User · Answer

There are several reasons this can happen   Some of these I found here  others I discovered on my own    If the property is named something other than Id  you need to add the  Key  attribute to it  The key needs to be a property  not a field  The key needs to be public The key needs to be a CLS-compliant type  meaning unsigned types like uint  ulong etc  are not allowed  This error can also be caused by configuration mistakes

User · Answer

Make sure public members of student class are defined as properties w   get  set    yours are public variables - a common mistake   Place a  Key  annotation on top of your chosen property

User · Answer

The Model class should be changed to    using System Collections Generic  using System Linq  using System Web  using System ComponentModel DataAnnotations Schema  using System ComponentModel DataAnnotations   namespace MvcApplication1 Models        Table  studentdetails        public class student                Key          public int RollNo   get  set             public string Name   get  set             public string Stream   get  set             public string Div   get  set

User · Answer

i know that this post is late but this solution helped me        Key       Column Order   0       public int RoleId   get  set      added  Column Order   0   after  Key   can be added by increment by 1        Key       Column Order   1       public int RoleIdName   get  set      etc

User · Answer

The reason why EF framework prompt  no key  is that EF framework needs a primary key in database  To declaratively tell EF which property the key is  you add a  Key  annotation  Or  the quickest way  add an ID property  Then  the EF framework will take ID as the primary key by default

User · Answer

Using the  key  didn t work for me but using an id property does it  I just add this property in my class   public int id  get  set

[c#] EntityType has no key defined error

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