Comparison of LINQ sorting methods with lambda sorting and the use of order by order and ThenBy

Follow the entity classes of the previous article with the EF operation Class code. Add a few data to the database

The sort method of Linq, the following example is based on Roleid ascending, name descending

Efcontext<member> Efmembercontext =NewEfcontext<member>();varMemberSet = Efmembercontext.set<member> (). Include ("Role");varMemberlist = fromMinchMemberSet byM.roleid Ascending, M.name descendingSelectm;foreach(Member Iteminchmemberlist) {Console.WriteLine ("{0},role:{1}", item. Name,item. Role.name);}

The output results are as follows:

The SQL Profiler is as follows:

The same way, if you sort by lambda, guess the following,

 efcontext<member> efmembercontext = new  efcontext<member> ();  var  memberset = efmembercontext.set<member> (). Include ( " role   "  var  memberlist = Memberset.orderby (M = M.roleid). OrderByDescending (M => m.name);  foreach  (Member item in   Memberlist) {Console.WriteLine ( Span> " {0},role:{1}   " ,item. Name,item. Role.name);}   

Running the program finds inconsistencies with the LINQ approach,

SQL profile is as follows:

After discovering successive calls to order or orderbydescending, the last one is sorted, and ThenBy is in handy.

ThenBy the results are sorted two times after using the order or orderbydescending

 efcontext<member> efmembercontext = new  efcontext<member> ();  var  memberset = efmembercontext.set<member> (). Include ( " role   "  var  memberlist = Memberset.orderby (M = M.roleid). ThenByDescending (M => m.name);  foreach  (Member item in   Memberlist) {Console.WriteLine ( Span> " {0},role:{1}   " ,item. Name,item. Role.name);}   

If you want to sort more than one column in a database, you can first order (or orderbydescending) the ThenBy (or thenbydescending). You can also specify more than one property directly in order or orderbydescending, so that the resulting SQL is the sort of multiple columns (sort-consistent asc/desc)

 efcontext<member> efmembercontext = new  efcontext<member> ();  var  memberset = efmembercontext.set<member> (). Include ( " role   "  var  memberlist = Memberset.orderby (m = new   foreach  (Member item in   Memberlist) {Console.WriteLine ( Span> " {0},role:{1}   " ,item. Name,item. Role.name);}   

Comparison of LINQ sorting methods with lambda sorting and the use of order by order and ThenBy