Searching for a range of dates in LINQ - linq

Question

I'm trying to do a search through a table via LINQ and Entity Framework CORE. I've got 2 text boxes startdate and enddate and a radio button set of 3 options created, modified and both.
This is the code I've produced based on Google searches and tutorials
switch(radCreatedModifiedBoth) {
case "b":
if (!String.IsNullOrEmpty(startDate)) {
if (!String.IsNullOrEmpty(endDate)) {
persons = persons.Where(ps => (
ps.CreatedDate >= Convert.ToDateTime(startDate + " 00:00:00") &&
ps.CreatedDate <= Convert.ToDateTime(endDate + " 23:59:59")
) || (
ps.ModifiedDate >= Convert.ToDateTime(startDate + " 00:00:00") &&
ps.ModifiedDate <= Convert.ToDateTime(endDate + " 23:59:59")
)
);
} else {
persons = persons.Where(ps => (
ps.CreatedDate >= Convert.ToDateTime(startDate + " 00:00:00")
||
ps.ModifiedDate >= Convert.ToDateTime(startDate + " 00:00:00")
)
);
}
} else if (!String.IsNullOrEmpty(endDate)) {
persons = persons.Where(ps => (
ps.CreatedDate >= Convert.ToDateTime(endDate + " 23:59:59")
||
ps.ModifiedDate >= Convert.ToDateTime(endDate + " 23:59:59")
)
);
}
break;
case "c":
if (!String.IsNullOrEmpty(startDate)) {
if (!String.IsNullOrEmpty(endDate)) {
persons = persons.Where(ps => (
ps.CreatedDate >= Convert.ToDateTime(startDate + " 00:00:00") &&
ps.CreatedDate <= Convert.ToDateTime(endDate + " 23:59:59")
)
);
} else {
persons = persons.Where(ps => (
ps.CreatedDate >= Convert.ToDateTime(startDate + " 00:00:00")
)
);
}
} else if (!String.IsNullOrEmpty(endDate)) {
persons = persons.Where(ps <= (
ps.CreatedDate >= Convert.ToDateTime(endDate + " 23:59:59")
)
);
}
break;
case "m":
if (!String.IsNullOrEmpty(startDate)) {
if (!String.IsNullOrEmpty(endDate)) {
persons = persons.Where(ps => (
ps.ModifiedDate >= Convert.ToDateTime(startDate + " 00:00:00") &&
ps.ModifiedDate <= Convert.ToDateTime(endDate + " 23:59:59")
)
);
} else {
persons = persons.Where(ps => (
ps.ModifiedDate >= Convert.ToDateTime(startDate + " 00:00:00")
)
);
}
} else if (!String.IsNullOrEmpty(endDate)) {
persons = persons.Where(ps <= (
ps.ModifiedDate >= Convert.ToDateTime(endDate + " 23:59:59")
)
);
}
break;
}
This code works but seems massively inefficient, not to mention adding the start and end time into the date as a string like this
startDate + " 00:00:00"
endDate + " 23:59:59"
just seems wrong. Is this the prescribed method or can anyone suggest a more efficient method preferably getting rid of the " 00:00:00"/" 23:59:59"
Thanks

Answer 1

You can simplify by pushing the tests to SQL - the conditional operator will be translated to SQL CASE WHEN since they aren't simple constants. Note that I assumed you have the endDate tests backwards in your code sample. Also you have a lot of repeated sub-expressions I consolidated to variables. Since you are using EF Core, there isn't a better way to handle date only comparisons then what you are using. In EF you can use a DbFunction, but it still isn't as good as converting your dates to the appropriate date+time so that indices can be used.
var hasStartDate = !String.IsNullOrEmpty(startDate);
var dtStartDate = hasStartDate ? Convert.ToDateTime(startDate + " 00:00:00") : DateTime.MinValue;
var hasEndDate = !String.IsNullOrEmpty(endDate);
var dtEndDate = hasEndDate ? Convert.ToDateTime(endDate + " 23:59:59") : DateTime.MinValue;
var chkCreatedDate = (radCreatedModifiedBoth == "b" || radCreatedModifiedBoth == "c");
var chkModifiedDate = (radCreatedModifiedBoth == "b" || radCreatedModifiedBoth == "m");
persons = persons.Where(ps => (chkCreatedDate ? (hasStartDate ? ps.CreatedDate >= dtStartDate : true) && (hasEndDate ? ps.CreatedDate <= dtEndDate : true) : true)
||
(chkModifiedDate ? (hasEndDate ? ps.ModifiedDate >= dtStartDate : true) && (hasEndDate ? ps.ModifiedDate <= dtEndDate : true) : true)
);