.net - C# abstract base class for common columns in LINQ -

this have far

using system; using system.collections.generic; using system.data.linq; using system.data.linq.mapping; using system.linq; using system.text;  namespace firelight.business {     public interface ibaseentity<k>     {         k id { get; }     }      /// <summary>     /// base business database connection object, primary key int     /// </summary>     /// <typeparam name="t">table name</typeparam>     public abstract class baseentity<t> : baseentity<t, guid> t : class, ibaseentity<guid>     {     }      /// <summary>     /// base business database connection object     /// </summary>     /// <typeparam name="t">table name</typeparam>     /// <typeparam name="k">primary key type</typeparam>     public abstract class baseentity<t,k> : ibaseentity<k> t : class, ibaseentity<k>     {         // avoids having declare ibaseconnection @ partial class level         [column(name = "id", canbenull = false, isprimarykey = true, isdbgenerated = true)]         public k id { get; set; } // { return default(k); }          public static table<t> table          {             { return linqutil.context.gettable<t>(); }          }          public static t searchbyid(k id)         {             return table.single<t>(t => t.id.equals(id));         }          public static void deletebyid(k id)         {             table.deleteonsubmit(searchbyid(id));             linqutil.context.submitchanges();         }     } } 

my problem mapping doesn't work:

data member 'system.guid [or system.int32] id' of type 'x' not part of mapping type 'x'. member above root of inheritance hierarchy?

before trying map attributes, got instead:

could not find key member 'id' of key 'id' on type 'x'. key may wrong or field or property on 'x' has changed names.

i tried changing k guid , works, why? don't see how generic-typing issue here

i'm not entirely sure needed interface either, don't remember why added it.

so, question be: how can make class work? want can access commonly named pk (id), has type k [which guid or int32], , refactor basic functions select , delete id

thanks!

edit:

this works

using system; using system.collections.generic; using system.data.linq; using system.linq;  namespace firelight.business {     public interface ibaseentity<k>     {         k id { get; set; }     }      /// <summary>     /// base business database connection object     /// </summary>     /// <typeparam name="t">table name</typeparam>     public abstract class baseentity<t> : ibaseentity<guid> t : class, ibaseentity<guid>     {         // avoids having declare ibaseconnection @ partial class level         public guid id { get; set; }          public static table<t> table          {             { return linqutil.context.gettable<t>(); }          }          public static t searchbyid(guid id)         {             return table.single<t>(t => t.id.equals(id));         }          public static void deletebyid(guid id)         {             table.deleteonsubmit(searchbyid(id));             linqutil.context.submitchanges();         }     } } 

what want same, replacing guid k , making class baseentity (so can use same class int32 , guid pks

what seeking not work linq sql. use inheritance linq sql, have make use of [inheritancemapping] attribute on base class. let's have base class called vehicle , sub-class called motorcycle:

[inheritancemapping(type = typeof(motorcycle), isdefault = true, code = 1)] [table] public class vehicle {     [column]     pubic string make { get; set; }      [column]     pubic string model { get; set; }      [column(isdiscriminator = true, name="vehicletypeid")]     public vehicletype vehicletype { get; set; } }  public class motorcycle : vehicle {     // implementation here } 

in order make inheritance work in linq sql, have apply [inheritancemapping] base class and have have discriminator column (e.g., vehicletype in above example). notice code in inheritancemapping "1" - means if vehicletype database "1" it'll create motorcycle sub-class. apply 1 [inheritancemapping] attribute on base class each sub-class you're supporting.

from purist standpoint, violation of oo because base class knows it's sub-classes. bit of weirdness typically puts people off little how linq sql implements inheritance. there have it.

update works:

public abstract class baseentity<t, k> : ibaseentity<k> t : class, ibaseentity<k> {     public abstract k id { get; set; }      public static table<t> table     {         { return context.gettable<t>(); }     }      public static t searchbyid(k id)     {         return table.single<t>(t => t.id.equals(id));     }      public static void deletebyid(k id)     {         table.deleteonsubmit(searchbyid(id));         context.submitchanges();     } } 

notice difference don't have [column] attribute on id property. notice made abstract. implementing class looks this:

[table(name = "dbo.contacts")] public class contact : baseentity<contact, int> {     [column]     public override int id { get; set; }     [column]     public string firstname { get; set; }     [column]     public string lastname { get; set; } } 

notice id property in class does have [column] attribute , i'm overriding abstract propety. verified works.

having said that, there couple of reasons why question current design. first you've got data access methods part of entity , many people (including myself) consider violation of separation of concerns. introduce repository pattern here , have repository each entity - make repository generic based on type , key. other thing weird above approach baseentity has id property , sub-class (in example contact class) has property of id (to make linq sql happy). had make id property in base class abstract , override in implementor. violates dry because i'll have each entity. thing result of hoops have jump through make linq sql happy. will work! :)