ef code first - When exactly does Entity Framework Fire a SQL Command? -

suppose have code like:

public void testwhensqlfires() {     var db = new db(); // ef dbcontext     var items = db.simpleobjects; // simpleobject implements interface iid     var byid = whereid(items, 1);     var array = byid.toarray(); }  protected ienumerable<iid> whereid(ienumerable<iid> items, int id) {     return items.where(i => i.id == id); } 

at line in testwhensqlfires() sql run against database?

(this question spun off comments on this answer)

one way find out , test yourself:

open sql server management studio, open new query, select database ef running against , run query:

select top 10 deqs.last_execution_time [time], dest.text [query] sys.dm_exec_query_stats deqs cross apply sys.dm_exec_sql_text(deqs.sql_handle) dest order deqs.last_execution_time desc 

this tells past 10 queries have run against database.

set breakpoint on first line of testwhensqlfires(), run code, run above query after stepping on each line. you'll find:

// c# line 1 var db = new db();  --sql line 1 select table_schema schemaname, table_name name information_schema.tables     table_type = 'base table'  // c# line 2 var items = db.simpleobjects;  --sql line 2 select count(*) [sys].[databases] [name]=@1  select [groupby1].[a1] [c1] (     select count(1) [a1] [dbo].[__migrationhistory] [extent1] ) [groupby1]  (@1 nvarchar(4000))select top (1) [project1].[c1] [c1],     [project1].[migrationid] [migrationid],     [project1].[model] [model]  (         select [extent1].[migrationid] [migrationid],             [extent1].[model] [model], 1 [c1]             [dbo].[__migrationhistory] [extent1]      )  [project1]  order [project1].[migrationid] desc  // c# line 3 var byid = whereid(items, 1);  --sql line 3  // c# line 4 var array = byid.toarray();  --sql line 4 select [extent1].[id] [id], [extent1].[stuff] [stuff]     [dbo].[simpleobject] [extent1] 

the final sql query ef fetching data. prior queries warming - verifying database exists, it's using ef5 migration history, , matches current migration history hash.

so answer - 4th line, after .toarray() called (or call enumerates collection, .tolist(), foreach, etc). notably passing method accepts ienumerable, if there's specific generic involved, not enumerate collection, , not fire off sql earlier necessary.