SQL to Linq group by count - sql

Question

I have a single column in a table to count specific rows. The sql query is as below:
SELECT
CASE
WHEN trail LIKE 'ClassA%' THEN 'ClassA'
WHEN trail LIKE 'ClassB%' THEN 'ClassB'
WHEN trail LIKE 'SemA%' THEN 'SemesterA'
WHEN trail LIKE 'SemB%' THEN 'SemesterB'
END AS Logs
, COUNT(*) AS Count
FROM Logs where s_date >= 'from date from UI' and e_date <= 'to date from ui'
GROUP BY
CASE
WHEN trail LIKE 'ClassA%' THEN 'ClassA'
WHEN trail LIKE 'ClassB%' THEN 'ClassB'
WHEN trail LIKE 'SemA%' THEN 'SemesterA'
WHEN trail LIKE 'SemB%' THEN 'SemesterB'
END
The above query result in sql fine as
ClassA 20
ClassB 5
SemesterA 2
SemesterB 50
Now, I need to change this sql to Linq with a date filter (from date, to date).
Please suggest change in query to simplyfy it.
Thanks
Tried:-
var data = _db.Logs.Where(p => p.trail.StartsWith("ClassA") && (p.SDate.Date >= CDate.Date && p.SDate.Date <= FDate.Date)).GroupBy(p => p.trail.StartsWith("ClassA")).Select(s =>
new
{
source = "Class - A total",
percentage = s.Count()
}).Union(_db.Logs.Where(p => p.trail.StartsWith("ClassB") && (p.SDate.Date >= CDate.Date && p.SDate.Date <= FDate.Date)).GroupBy(p => p.trail.StartsWith("ClassB")).Select(s =>
new
{
source = "Class - B total",
percentage = s.Count()
}).Union(_db.Logs.Where(p => p.trail.StartsWith("SemesterA") && (p.SDate.Date >= CDate.Date && p.SDate.Date <= FDate.Date)).GroupBy(p => p.trail.StartsWith("SemesterA")).Select(s =>
new
{
source = "Semester - A total",
percentage = s.Count()
}).Union(_db.Logs.Where(p => p.trail.StartsWith("SemesterB") && (p.SDate.Date >= CDate.Date && p.SDate.Date <= FDate.Date)).GroupBy(p => p.trail.StartsWith("SemesterB")).Select(s =>
new
{
source = "Semester - B total",
percentage = s.Count()
})))).ToList();

Answer 1

Try storing all the interesting starting keys in an enumerable of some sort and then using the built in group by method overload which outputs a result mapped from the key,group pairs (c.f. https://msdn.microsoft.com/en-us/library/vstudio/bb549393(v=vs.100).aspx)
string[] startingKeys = new string[] {"ClassA","ClassB","SemsterA","SemesterB"};
var data =_db.Logs.Where(p=>(p.SDate.Date >= CDate.Date && p.SDate.Date <= FDate.Date)&&startingKeys.Any(k=>p.Logs.StartsWith(k))).GroupBy(p=>startingKeys.Where(k=>p.Logs.StartsWith(k)).First(),(key,items)=>new {source=key,count = items.Count()})
One advantage of this method is you can change the starting keys at runtime if you feel like it.