Conditionally Exclude Child Property in Entity Framework Query -


given following object graph

public class bar {     public guid id {get;set;}     public string somebar {get;set;} }  public class foo {     public guid id {get;set;}     public string foostring {get; set;}     public ilist<bar> bars {get;set;} }

how conditionally exclude bars property entity framework doesn't load entire object graph?

// thoughts public task<foo> getfoobyidasync(guid id, bool includebars)  {     var query = _db.foos.where(f => f.id == id);     if(!includebars)     {         return query.select(f=> new foo{             id = f.id,             foostring = f.foostring         }).tolistasync();     } else {         return query.tolistasync();     } }

just conditionally add include(f => f.bars) query expression. this:

using system; using system.collections.generic; using system.componentmodel.dataannotations.schema; using system.data.common; using system.data.entity; using system.data.entity.modelconfiguration; using system.data.sqlclient; using system.linq; using system.threading.tasks;   namespace consoleapp8 {     public class bar     {         public guid id { get; set; }         public string somebar { get; set; }     }      public class foo     {         public guid id { get; set; }         public string foostring { get; set; }         public ilist<bar> bars { get; set; }     }      class db: dbcontext     {          public dbset<foo> foos { get; set; }         public dbset<bar> bar { get; set; }          public async task<foo> getfoobyidasync(guid id, bool includebars)         {             var query = (iqueryable<foo>)foos.asnotracking();              if (includebars)             {                 query = query.include(f => f.bars);             }              query = query.where(f => f.id == id);              var results = await query.tolistasync();              return results.firstordefault();                     }     }        class program     {                static void main(string[] args)         {              database.setinitializer(new dropcreatedatabasealways<db>());               using (var db = new db())             {                 db.database.initialize(false);                 db.database.log = m => console.writeline(m);                  var r1 = db.getfoobyidasync(guid.empty, false).result;                 var r2 = db.getfoobyidasync(guid.empty, true).result;              }             console.writeline("hit key exit");             console.readkey();           }     } }

outputs

opened connection asynchronously @ 9/11/2017 11:37:26 pm -05:00  select     [extent1].[id] [id],     [extent1].[foostring] [foostring]     [dbo].[foos] [extent1]     [extent1].[id] = @p__linq__0   -- p__linq__0: '00000000-0000-0000-0000-000000000000' (type = guid, isnullable = false)  -- executing asynchronously @ 9/11/2017 11:37:26 pm -05:00  -- completed in 22 ms result: sqldatareader    closed connection @ 9/11/2017 11:37:26 pm -05:00  opened connection asynchronously @ 9/11/2017 11:37:26 pm -05:00  select     [project1].[c1] [c1],     [project1].[id] [id],     [project1].[foostring] [foostring],     [project1].[c2] [c2],     [project1].[id1] [id1],     [project1].[somebar] [somebar]     ( select         [extent1].[id] [id],         [extent1].[foostring] [foostring],         1 [c1],         [extent2].[id] [id1],         [extent2].[somebar] [somebar],         case when ([extent2].[id] null) cast(null int) else 1 end [c2]          [dbo].[foos] [extent1]         left outer join [dbo].[bars] [extent2] on [extent1].[id] = [extent2].[foo_id]         [extent1].[id] = @p__linq__0     )  [project1]     order [project1].[id] asc, [project1].[c2] asc   -- p__linq__0: '00000000-0000-0000-0000-000000000000' (type = guid, isnullable = false)  -- executing asynchronously @ 9/11/2017 11:37:26 pm -05:00  -- completed in 2 ms result: sqldatareader    closed connection @ 9/11/2017 11:37:26 pm -05:00  hit key exit

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