c# - Multi-Mapper in Dapper one to many relations -

i trying value of database relation 1 many have object this

student

[table("student")]     public class student  : istudent     {              public int id { get; set; }         public string lastname { get; set; }         public string firstmidname { get; set; }         public datetime? enrollmentdate { get; set; }          [write(false)]         public ienumerable<enrollment> enrollments { get; set; }     } 

enrollment

[table("enrollment")]     public class enrollment     {         public int id { get; set; }         public int courseid { get; set; }         public int studentid { get; set; }         public string grade { get; set; }         public virtual course course { get; set; }         public virtual student student { get; set; }     } 

course

[table("course")] public class course {        public int id { get; set; }     public string title { get; set; }     public int credits { get; set; }     public virtual ienumerable<enrollment> enrollments { get; set; } } 

here dapper code

_connection = connect.getopenconnection();         const string query = @"select * student stu id = @id " +                              "select * enrollment enr enr.studentid in (select id student stu id = @id) " +                              "select * course cou cou.id in (select courseid enrollment studentid = @id)";          var result = _connection.querymultiple(query, new { id = id })             .map<student, enrollment, course, int>(                 student => student.id,                      enrollment => enrollment.studentid,                 course=>course.id,                 (student, enrollments) => student.enrollments = enrollments ,                 (student, courses) => student.enrollments.foreach(s=>courses.foreach(x=>s.course.title = x.title) )             ).firstordefault(); 

as per instruction here have extend 3 level hierarchy cant make work

here gridreader mapper

public static ienumerable<tfirst> map<tfirst, tsecond, tthird, tkey>         (         sqlmapper.gridreader reader,         func<tfirst, tkey> firstkey,         func<tsecond, tkey> secondkey,         func<tthird, tkey> thirdkey,         action<tfirst, ienumerable<tsecond>> addsecond,         action<tfirst, ienumerable<tthird>> addthird         )     {         var result = reader.read<tfirst>().tolist();          var secondmap = reader             .read<tsecond>()             .groupby(s=>secondkey(s))             .todictionary(g => g.key, g => g.asenumerable());          var thirdmap = reader            .read<tthird>()            .groupby(t => thirdkey(t))            .todictionary(g => g.key, g => g.asenumerable());                foreach (var item in result)         {             ienumerable<tthird> third;             if (thirdmap.trygetvalue(firstkey(item), out third))             {                 addthird(item, third);             }              ienumerable<tsecond> second;             if (secondmap.trygetvalue(firstkey(item), out second))             {                 addsecond(item, second);             }          }            return result.tolist();     } 

when run app here result id of 1 notice course title have no value. hope can me thank you.

update 1

i notice getting null value here, doesnt inside if statement

ienumerable<tsecond> second;         if (secondmap.trygetvalue(firstkey(item), out second))         {             addsecond(item, second);         } 

update 2

i solve problem here do

var ctr = 0;         var mapped2 = conn.querymultiple(query, new {id})             .map<student, enrollment, course, int>(                 student => student.studentid,                 enrollment => ctr = enrollment.studentid,                 course=>course.courseid = ctr,                 ((student, enrollments) => { student.enrollments = enrollments; }),                 ((student, courses) => courses.tolist().foreach(s=> student.enrollments.tolist().foreach(x=>x.course = new course                 {                     title = s.title                 })))); 

notice added ctr value of courseid in enrollment => ctr = enrollment.studentid. ok face problem, how value of courses here code

((student, courses) => courses.tolist().foreach(s=> student.enrollments.tolist().foreach(x=>x.course = new course { title = s.title }))

i getting last value

here how solve problem

as above update 2 details added variable ctr value of courseid enrollment , pass course right value. after face problem how pass value of course student.enrollment.course here's how figure out.

i create variable var enrolllst = new list<enrollment>(); hold value of enrollment first action

((student, enrollments) =>                 {                     enrolllst = enrollments.tolist();                 }), 

second action

((student, courses) =>                 {                     var ctrid = 0;                       courses.tolist().foreach(cour =>                     {                         if (cour != null)                         {                             enrolllst[ctrid].course = cour;                             ctrid++;                         }                         else                         {                             enrolllst[ctrid].course = null;                             ctrid++;                         }                        });                     student.enrollments = enrolllst;                 })).firstordefault();  

below whole code

_connection = connect.getopenconnection();         const string query = "select * student stu studentid = @id  " +                              "select * enrollment enr enr.studentid in ( select studentid student stu studentid = @id)  " +                              "select * course cou cou.courseid in (select courseid enrollment studentid = @id)";          var enrolllst = new list<enrollment>();         var ctr = 0;         var result = _connection.querymultiple(query, new { id })             .map<student, enrollment, course, int>(                 student => student.studentid,                 enrollment => ctr = enrollment.studentid,                 course => course.courseid = ctr,                 ((student, enrollments) =>                 {                     enrolllst = enrollments.tolist();                 }),                 ((student, courses) =>                 {                     var ctrid = 0;                       courses.tolist().foreach(cour =>                     {                         if (cour != null)                         {                             enrolllst[ctrid].course = cour;                             ctrid++;                         }                         else                         {                             enrolllst[ctrid].course = null;                             ctrid++;                         }                        });                     student.enrollments = enrolllst;                 })).firstordefault();  

gridreader mapper extended 3 level hierarchy instructed here

public static ienumerable<tfirst> map<tfirst, tsecond, tthird, tkey>         (         sqlmapper.gridreader reader,         func<tfirst, tkey> firstkey,         func<tsecond, tkey> secondkey,         func<tthird, tkey> thirdkey,         action<tfirst, ienumerable<tsecond>> addsecond,         action<tfirst, ienumerable<tthird>> addthird         )     {         var result = reader.read<tfirst>().tolist();          var secondmap = reader             .read<tsecond>()             .groupby(secondkey)             .todictionary(g => g.key, g => g.asenumerable());          var thirdmap = reader            .read<tthird>()            .groupby(thirdkey)            .todictionary(g => g.key, g => g.asenumerable());               foreach (var item in result)         {             ienumerable<tsecond> second;             if (secondmap.trygetvalue(firstkey(item), out second))             {                 addsecond(item, second);             }              ienumerable<tthird> third;             if (thirdmap.trygetvalue(firstkey(item), out third))             {                 addthird(item, third);             }           }           return result.tolist();     }