c# - if-else spipping search strategy in LINQ query -

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• second linq filter multiple conditions 2 answers

i trying filter multiple attribute database. filtering 3 attributes. may empty or key in combination. have tried code, working fine when filtered in 3 steps,

ienumerable<employee> itemslist = _db.employees.asenumerable().where(e => e.role == 2).orderbydescending(e => e.employeeid);  if (!string.isnullorempty(searchkeybyname))             {                 itemslist = itemslist.where(e => e.firstname.tolower().startswith(searchkeybyname.trim().tolower()) || e.lastname.tolower().startswith(searchkeybyname.trim().tolower()) || (e.firstname + " " + e.lastname).tolower().startswith(searchkeybyname.trim().tolower()));                 viewbag.search_fullname = searchkeybyname;             }             if (!string.isnullorempty(searchkeybydepartment))             {                 itemslist = itemslist.where(e => e.department.departmenttitle.tolower().startswith(searchkeybydepartment.trim().tolower()));                 viewbag.search_department = searchkeybydepartment;             }             if (!string.isnullorempty(searchkeybydesignation))             {                 itemslist = itemslist.where(e => e.designation.tolower().startswith(searchkeybydesignation.trim().tolower()));                 viewbag.search_designation = searchkeybydesignation;             } 

but want minimize 3 if condition linq, have tried 1 of using code

ienumerable<employee> itemslist2 = (from e in _db.employees.asenumerable()                                                 e.role == 2                                                 (!string.isnullorempty(searchkeybyname) && (e.firstname.trim().tolower().startswith(searchkeybyname.trim().tolower()) || e.lastname.tolower().startswith(searchkeybyname.trim().tolower()) || (e.firstname + " " + e.lastname).tolower().startswith(searchkeybyname.trim().tolower())))                                                 select e).orderbydescending(e => e.employeeid); 

but filtering result being null/empty. 1st 1 working well. mention that, search key may empty, need peek values when key provided take key findings one.

the problem &&; requiring searchkeybyname not empty/null using that. filter should keep records if searchkeybyname null or missing or use in search otherwise: searchkeybyname.isnullorempty() || (rest of it). in case, can simplify out using null coalescing, since every string starts empty string:

var itemslist2 =     e in _db.employees     let loweredsearch = (searchkeybyname ?? "").trim().tolower()              e.role == 2         && (             (e.firstname + " " + e.lastname).tolower().startswith(loweredsearch)              || e.lastname.tolower().startswith(loweredsearch)         )     orderby e.employeeid descending     select e; 

but more efficient:

var itemslist2 =     e in _db.employees     let loweredsearch = (searchkeybyname ?? "").trim().tolower()              e.role == 2         && (             loweredsearch == string.empty             || (e.firstname + " " + e.lastname).tolower().startswith(loweredsearch)              || e.lastname.tolower().startswith(loweredsearch)         )     orderby e.employeeid descending     select e;