How to compare string data to time - sql

Question

I have data type in string and the time is like 06:00A, 09:00P, etc. I would like to query data from 6am to 12pm, how do I convert the string data to time format and query it in linq to sql?

Answer 1

Use DateTime.ParseExact or DateTime.TryParseExact to convert the string to a date. If you can't guarantee that the string version of your time is always going to be correct, stick to the TryParseExact version.
Once you have it converted to date, query as normal.
Example at: https://dotnetfiddle.net/MDnERt
Edited after response:
If you are using the code as written against EntityFramework then no, this will not work. (Please also note that there is a big difference between Linq To SQL and Entity Framework, but the same concepts apply, to some degree)
ORMs that support LINQ are actually converting your where clauses into an Expression which is then translated by the ORM into SQL. You will get a NotSupported exception, or something similar.
Is there some reason why the table in question is using that time format? Why would you not just use a datetime in the table? There is also the option of using the time datatype in sql server (assuming you are targetting sql server) which is mapped to the TimeSpan type in .net.
You would define your table in Sql server like:
create table log ( data varchar(20), logtime time )
and the LINQ expression would look something like:
from x in Logs
where x.Logtime >= new TimeSpan(6,0,0) && x.Logtime <= new TimeSpan(12,0,0)
select x
Now we are getting into actual design questions, though, which is off topic. :)

Answer 2

I'd suggest writing own parser and represent times as TimeSpan:
TimeSpan? ToTimeSpan(string str)
{
// get A or P at the end
var amPm = str.Last();
int hrs, mins;
try
{
hrs = int.Parse(str.Substring(0, 2));
mins = int.Parse(str.Substring(3, 2));
}
catch
{
return null;
}
switch (amPm)
{
case 'P': hrs += 12; break;
case 'A': break;
default: return null;
}
return new TimeSpan(hrs, mins, 0);
}