c# - AutoMapper flatten nested collections -

i try figure out how flatten collection of merchants, each containing collection of orders flat list of orderviewmodels.

here dto:

public class merchant {     public string merchantname { get; set; }     public list<order> orders { get; set; } }  public class order {     public string orderid { get; set; } } 

and here's view model:

public class orderviewmodel {     public string merchantname { get; set; }     public string orderid { get; set; } } 

my goal flatten list<merchant> list<orderviewmodel> whereas following test structure should result in 6 view models:

var mymerchants = new list<merchant> {     new merchant     {         merchantname = "merchant x",         orders = new list<order>         {              new order { orderid = "order 1"},              new order { orderid = "order 2"},              new order { orderid = "order 3"}         }     },     new merchant     {         merchantname = "merchant y",         orders = new list<order>         {             new order { orderid = "order 4"},             new order { orderid = "order 5"},             new order { orderid = "order 6"}         }     }  };   var models = mapper.map<list<orderviewmodel>>(mymerchants); 

because cardinality of root objects isn't 1:1, (i.e. 2 root merchants need map 6 orderviewmodels), may need resort custom typeconverter , operate @ collection level, can use .selectmany flattening:

public class mytypeconverter : itypeconverter<ienumerable<merchant>, list<orderviewmodel>> {     public list<orderviewmodel> convert(resolutioncontext context)     {         if (context == null || context.issourcevaluenull)             return null;          var source = context.sourcevalue ienumerable<merchant>;          return source             .selectmany(s => s.orders               .select(o => new orderviewmodel               {                   merchantname = s.merchantname,                   orderid = o.orderid               }))               .tolist();     } } 

which can bootstrap:

mapper.createmap<ienumerable<merchant>, list<orderviewmodel>>()     .convertusing<mytypeconverter>(); 

and mapped such:

var models = mapper.map<list<orderviewmodel>>(mymerchants);