Hi to all

i wrote a module on dnn8 ,i used dnn service framework and petapoco for module datalayer.

i used the petapoco like below code:

PetaPoco.Database db = new PetaPoco.Database();
            DotNetNuke.Data.PetaPoco.PetaPocoRepository<TrainingCenterInfo> ppr = new DotNetNuke.Data.PetaPoco.PetaPocoRepository<TrainingCenterInfo>(db,
                                                                                  PetaPoco.Mappers.GetMapper((new TrainingCenterInfo()).GetType()));

in first step or in first call this method is true and worked to fetch data!!!

but on over call above methode,i get the error,the error message is : An item with the same key has already been added.

and the logged error in Log viewer is :

AbsoluteURLReferrer:http://localhost:85/%D9%86%D8%B4%D8%B1%D8%B4%D9%87%D8%B1/tabid/105/ctl/AddStudent/mid/494/Default.aspx

UserAgent:Mozilla/5.0 (Windows NT 6.1; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0

DefaultDataProvider:DotNetNuke.Data.SqlDataProvider, DotNetNuke

ExceptionGUID:741f74e4-4241-4eb1-9685-4f612722c9d6

InnerException:An item with the same key has already been added.

FileName:

FileLineNumber:0

FileColumnNumber:0

Method:System.Collections.Generic.Dictionary`2.Insert

StackTrace:

Message:

DotNetNuke.Services.Exceptions.PageLoadException: An item with the same key has already been added. ---> System.ArgumentException: An item with the same key has already been added.
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at PetaPoco.Mappers.RegisterInternal(Object typeOrAssembly, IMapper mapper)
   at PetaPoco.Mappers.Register(Type type, IMapper mapper)
   --- End of inner exception stack trace ---

Source:

Server Name : 002-PC

where is my mistak? and what do i do for use petapoco in my module?

Thanks for your attention's and your replay.