var ch = _context.xxtu_nintex_emp_data_v
         .Where(o => o.LOGIN_USER_NAME ==userId.ToUpper())
         .Select(emp => new
         { OTHERMOBILENO = emp.OTHERMOBILENO ?? "" })
         .ToList().SingleOrDefault();

the result is

when use toList() I get what I want but it is so slow

var ch = _context.xxtu_nintex_emp_data_v.ToList()
         .Where(o => o.LOGIN_USER_NAME ==userId.ToUpper())
         .Select(emp => new
         { OTHERMOBILENO = emp.OTHERMOBILENO ?? "" })
         .ToList().SingleOrDefault();

the result is

I use code first approach api and Microsoft.EntityFrameworkCore

CodePudding user response：

Some things you could try

1. Call ToList after the condition, to only fetch a subset of data from the Database

    var ch = _context.xxtu_nintex_emp_data_v
         .Where(o => o.LOGIN_USER_NAME == userId.ToUpper())
         .ToList() //<-- here
         .Select(emp => new
         { OTHERMOBILENO = emp.OTHERMOBILENO ?? "" })
         .ToList().SingleOrDefault();
   

2. Move the Select after the Last ToList call

    var ch = _context.xxtu_nintex_emp_data_v
         .Where(o => o.LOGIN_USER_NAME == userId.ToUpper())
         //<-- re-arrange ToList/Select
         .ToList()
         .Select(emp => new { OTHERMOBILENO = emp.OTHERMOBILENO ?? "" }) 
         //<-- 
         .SingleOrDefault();
   

3. Re-arrange it a bit more

    var emp = _context.xxtu_nintex_emp_data_v
         .Where(o => o.LOGIN_USER_NAME == userId.ToUpper())
         .SingleOrDefault();
   
    var ch = new { OTHERMOBILENO = emp?.OTHERMOBILENO ?? "" };