How to generate and auto increment Id with Entity Framework

Question

Revised entire post   I m trying to post the following JSON POST request via Fiddler    Username  Bob   FirstName  Foo   LastName  Bar   Password  123   Headline  Tuna     However I m getting this error   Message  Cannot insert the value NULL into column  Id   table  xxx f8dc97e46f8b49c2b825439607e89b59 dbo User   column does not allow nulls  INSERT fails  r nThe statement has been terminated   string   Though if I manually send a random Id along with the request then all is good  Like so    Id  1   Username  Bob   FirstName  Foo   LastName  Bar   Password  123   Headline  Tuna     Why does Entity Framework not generate and auto increment the Id s  My POCO class is as follows   public class User        Key       DatabaseGenerated DatabaseGeneratedOption Identity       public string Id   get  set        public string Username   get  set        public string FirstName   get  set        public string LastName   get  set        public string Password   get  set        public string Headline   get  set        public virtual ICollection lt Connection gt  Connections   get  set        public virtual ICollection lt Address gt  Addresses   get  set        public virtual ICollection lt Phonenumber gt  Phonenumbers   get  set        public virtual ICollection lt Email gt  Emails   get  set        public virtual ICollection lt Position gt  Positions   get  set       public class Connection       public string ConnectionId   get  set        public int UserId   get  set        public virtual User User   get  set       public class Phonenumber       public string Id   get  set        public string Number   get  set        public int Cycle   get  set        public int UserId   get  set        public User User   get  set        Here is the controller method  When in debug mode and I send the request via Fiddler it breaks at db SaveChanges    and gives the error seen a bit above          POST api xxx create      ActionName  create        public HttpResponseMessage PostUser User user                if  ModelState IsValid                        db Users Add user               db SaveChanges                 HttpResponseMessage response   Request CreateResponse HttpStatusCode Created  user               response Headers Location   new Uri Url Link  DefaultApi   new   id   user Id                  return response                    else                       return Request CreateErrorResponse HttpStatusCode BadRequest  ModelState                     What s wrong    Solution  Change string Id to int instead and remove Data annotations  Renamed the Id to UserId  still following convention  and made changes where necessary in other POCO s to match up with the changes

User · Accepted Answer

This is a guess     Is it because the ID is a string  What happens if you change it to int   I mean    public int Id   get  set

User · Answer

You have a bad table design  You can t autoincrement a string  that doesn t make any sense  You have basically two options   1   change type of ID to int instead of string 2   not recommended    - handle autoincrement by yourself  You first need to get the latest value from the database  parse it to the integer  increment it and attach it to the entity as a string again  VERY BAD idea  First option requires to change every table that has a reference to this table  BUT it s worth it

[c#] How to generate and auto increment Id with Entity Framework

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