entity framework - EF: OrderBy is not working when I define a delegate with the same signature -

i've replaced sqldatasource objectdatasource. here's portion of select method

func<user, string> sortbydlg = (u) => {   string sortstr = string.isnullorempty(sortcolumn) ? "username" : sortcolumn;   return sortstr; };  var users = db.users.orderby(sortbydlg).tolist(); 

the first time page loads, want rows sorted username, after column selected.

when run code, no sorting happening. works when put anonymous method: orderby(u => u.username).

here's complete method

public static list<userviewmodel> getalluserviewmodels(string sortcolumn) {   using (var db = mydbcontext.create())   {     var model = new list<userviewmodel>();     func<user, string> sortbydlg = (u) =>     {         string sortstr = string.isnullorempty(sortcolumn) ? "username" : sortcolumn;           return sortstr;     };      var users = db.users.orderby(sortbydlg).tolist();     foreach (var item in users)     {         var u = new userviewmodel         {            userid = item.id,            first_name = item.firstname,            last_name = item.lastname,            telephone = item.telephone,            //more here ...          };           model.add(u);        }        return model;      }     } 

thanks helping

this how it, because find simple understand (without using expression trees):

public static list<userviewmodel> getalluserviewmodels(string sortcolumn) {   using (var db = mydbcontext.create())   {     var query = db.users.asqueryable();     switch(string.isnullorempty(sortcolumn) ? "username" : sortcolumn)     {        case "username": query=query.orderby(u=>u.username); break;        case "firstname": query=query.orderby(u=>u.firstname); break;        ... more ...     }     var model = query.select(u=> new userviewmodel {            userid = item.id,            first_name = item.firstname,            last_name = item.lastname,            telephone = item.telephone,            //more here ...          }).tolist();     return model;   } } 

actually, create functions getallusers returns iqueryable<user>, separate extension method iqueryable<user> orderbycolumn(this iqueryable<user> u,string sortcolumn), , extension ienumerable<userviewmodelitem> toviewmodel(this iqueryable<user> u), , use them like: var result = getallusers().orderbycolumn("username").toviewmodel();

// db defined elsewhere (repository pattern?)     public iqueryable<user> getallusers() {     return db.users.asqueryable(); }  public static iqueryable<user> orderbycolumn(this iqueryable<user> u,string sortcolumn) {     switch(string.isnullorempty(sortcolumn) ? "username" : sortcolumn)     {        case "username": return u.orderby(u=>u.username); break;        case "firstname": return u.orderby(u=>u.firstname); break;        ... more ...     } }  public static ienumerable<userviewmodelitem> toviewmodel(this iqueryable<user> users) {     return users.select(u=> new userviewmodelitem {            userid = item.id,            first_name = item.firstname,            last_name = item.lastname,            telephone = item.telephone,            //more here ...          }).tolist(); }