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Refactor and reduce cyclomatic complexity with LINQ

I have a method that I feel like could be refactored more efficiently with LINQ.
The purpose of the function is to use some logic to determine which phone number to return. The logic is: Any returned number must be sms_capable. If a number was last used for an rx, use it, otherwise return the first valid number by type in this order: Other, Home, Office
string GetDefaultSMSPhoneNumber(IEnumerable<PhoneNumbers> patientNumbers)
{
const int PHONE_TYPE_HOME = 1;
const int PHONE_TYPE_OFFICE = 3;
const int PHONE_TYPE_OTHER = 9;
var phoneNumberByType = patientNumbers.Where(p => p.sms_capable == 1).GroupBy(p => p.phone_type_id);
// Select the phone number last used in creating a prescription
if (patientNumbers.Where(p => p.sms_capable == 1 && p.last_used_for_rx == 1).Count() > 0)
{
return patientNumbers.Where(p => p.sms_capable == 1 && p.last_used_for_rx == 1).FirstOrDefault().phone_number;
}
// If no number has been used, select a configured SMS number in the following order (Other, Home, Office)
if (patientNumbers.Where(p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_OTHER).Count() > 0)
{
return patientNumbers.Where(p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_OTHER).FirstOrDefault().phone_number;
}
// If no number has been used, select a configured SMS number in the following order (Other, Home, Office)
if (patientNumbers.Where(p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_HOME).Count() > 0)
{
return patientNumbers.Where(p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_HOME).FirstOrDefault().phone_number;
}
// If no number has been used, select a configured SMS number in the following order (Other, Home, Office)
if (patientNumbers.Where(p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_OFFICE).Count() > 0)
{
return patientNumbers.Where(p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_OFFICE).FirstOrDefault().phone_number;
}
return string.Empty;
}
I know the first thing I can do is filter the list to only sms_capable numbers. I feel like I should be able to use .GroupBy to group the numbers by there type, but after they're grouped I'm not sure how to return the first non empty value? I feel like I'm looking for a way to coalesce in linq?
string GetDefaultSMSPhoneNumber(IEnumerable<PhoneNumbers> patientNumbers)
{
const int PHONE_TYPE_HOME = 1;
const int PHONE_TYPE_OFFICE = 3;
const int PHONE_TYPE_OTHER = 9;
var phoneNumberByType = patientNumbers.Where(p => p.sms_capable == 1).GroupBy(p => p.phone_type_id);
var phoneNumber = patientNumbers.FirstOrDefault(p => p.sms_capable == 1 && p.last_used_for_rx == 1)?.phone_number;
// Doesn't work
if (string.IsNullOrEmpty(phoneNumber))
{
var number = phoneNumberByType.FirstOrDefault(p => p.Key == PHONE_TYPE_OTHER && p.Where(x => !string.IsNullOrEmpty(x.phone_number)) ||
(p.Key == PHONE_TYPE_HOME && p.Where(x => !string.IsNullOrEmpty(x.phone_number)) ||
(p.Key == PHONE_TYPE_OFFICE && p.Where(x => !string.IsNullOrEmpty(x.phone_number))));
}

If you need matching against predicates in specific order you can create a collection of Func<PhoneNumbers, bool> and iterate it (also if PhoneNumbers is a class or record then you don't need Count, if it is not, better use Any instead of count):
string GetDefaultSMSPhoneNumber(IEnumerable<PhoneNumbers> patientNumbers)
{
const int PHONE_TYPE_HOME = 1;
const int PHONE_TYPE_OFFICE = 3;
const int PHONE_TYPE_OTHER = 9;
var predicates = new List<Func<PhoneNumbers, bool>>()
{
p => p.sms_capable == 1 && p.last_used_for_rx == 1,
p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_OTHER,
p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_HOME,
p => p.sms_capable == 1 && p.phone_type_id == PHONE_TYPE_OFFICE
}; // Can be moved to static field
// prevent potential multiple materialization of the source
var enumerated = patientNumbers as ICollection<PhoneNumbers> ?? patientNumbers.ToArray();
foreach (var predicate in predicates)
{
var firstOrDefault = enumerated.FirstOrDefault(predicate);
if (firstOrDefault is not null)
{
return firstOrDefault.phone_number;
}
}
return string.Empty;
}
Also in this particular case you can "prefilter" the enumerated with .Where(p => p.sms_capable == 1) to improve performance a bit:
// ...
var enumerated = patientNumbers
.Where(p => p.sms_capable == 1)
.ToArray();
var predicates = new List<Func<PhoneNumbers, bool>>()
{
p => p.last_used_for_rx == 1,
p => p.phone_type_id == PHONE_TYPE_OTHER,
p => p.phone_type_id == PHONE_TYPE_HOME,
p => p.phone_type_id == PHONE_TYPE_OFFICE
};
// ...

This isnt using linq, but you can refactor this by putting some of the complexity into their own methods
private IEnumerable<IGrouping<int, PhoneNumbers>> GetSmsCapablePhoneNumbersByType(IEnumerable<PhoneNumbers> patientNumbers)
{
return patientNumbers.Where(p => p.sms_capable == 1).GroupBy(p => p.phone_type_id);
}
private PhoneNumbers GetLastUsedSmsNumber(IEnumerable<PhoneNumbers> patientNumbers)
{
return patientNumbers.FirstOrDefault(p => p.sms_capable == 1 && p.last_used_for_rx == 1);
}
private PhoneNumbers GetFirstSmsNumberByType(IEnumerable<PhoneNumbers> patientNumbers, int phoneTypeId)
{
return patientNumbers.FirstOrDefault(p => p.sms_capable == 1 && p.phone_type_id == phoneTypeId);
}
public string GetDefaultSMSPhoneNumber(IEnumerable<PhoneNumbers> patientNumbers)
{
var phoneNumberByType = GetSmsCapablePhoneNumbersByType(patientNumbers);
var lastUsedSmsNumber = GetLastUsedSmsNumber(patientNumbers);
if (lastUsedSmsNumber != null)
{
return lastUsedSmsNumber.phone_number;
}
var defaultSmsNumber = GetFirstSmsNumberByType(patientNumbers, PHONE_TYPE_OTHER)
?? GetFirstSmsNumberByType(patientNumbers, PHONE_TYPE_HOME)
?? GetFirstSmsNumberByType(patientNumbers, PHONE_TYPE_OFFICE);
if (defaultSmsNumber != null)
{
return defaultSmsNumber.phone_number;
}
return string.Empty;
}
If you do it correctly, your method names should describe exactly whats happening, so when somone else reads your code they should be able to follow whats happening by reading the method names (This also means there is less need for comments)

LINQ Query with method syntax

My requirement is to make boolean value (IsPC=true) only if I found any value with IsCurrent = true from the list and second condition is to filter the list with G or W codes and third condition is to check the PCBNumber length ==15 with only one from the list.
How short can i able to reduce the below query using LINQ method syntax
below is my query
var CurrentQ= p.List.Where(x => x.IsConCurrent== true);
if (CurrentQ.Count() > 0)
{
var NCurrentQwithWorQ = p.List.Where(x => x.Codes == Codes.W|| x.Codes== Codes.Q).Count();
if (NCurrentQwithWorQ != null)
{
var PCBNumber = p.List.Where(x => x.PCBNumber .Length == 15).Count();
if (PCBNumber == 1)
{
isPC = true;
}
}
}

You can use all conditions in same query like below,
var PCBNumber= p.List.Where(x => x.IsConCurrent== true && (x.Codes == Codes.W|| x.Codes== Codes.Q) && x.PCBNumber.Length == 15);
if (PCBNumber !=null && PCBNumber.Count() == 1)
{
isPC = true;
}

I'm not trying to debug what you wrote, but isn't this really what you're looking for--that is, daisy-chaining your Where conditions?
var isPC = p.List.Where(x => x.IsConCurrent == true).Where(x => x.Codes == Codes.W || x.Codes == Codes.Q).Where(x => x.PCBNumber.Length == 15).Count() == 1;

Both solutions suggested above are correct.
p.List.Where(x => x.IsConCurrent== true && (x.Codes == Codes.W|| x.Codes== Codes.Q) && x.PCBNumber.Length == 15);
p.List.Where(x => x.IsConCurrent == true).Where(x => x.Codes == Codes.W || x.Codes == Codes.Q).Where(x => x.PCBNumber.Length == 15).Count()
Actually they are performed in the same way. The Where function does not force immediate iteration through the data source. Only when you execute the Count function, LINQ will process row by row and execute criterion by criterion to find out which values should be calculated.
I can only suggest you add the Take(2) operator after the where clause. In this case LINQ will stop after finding the first two rows that matches provided criterion and other rows will not be processed.
p.List.Where(x => x.IsConCurrent == true)
.Where(x => x.Codes == Codes.W || x.Codes == Codes.Q)
.Where(x => x.PCBNumber.Length == 15)
.Take(2).Count()

How to split string in c# linq?

I have this
from d in db.v_Report_CompanySearches
orderby d.InquiryLogID descending
where (mPersonName == null || d.AccountName.ToLower() == mPersonName || d.PersonName.ToLower() == mPersonName) &&
(mCompanyName == null || TagsContain(d.CompanySearchTerm, mCompanyName)) &&
d.CreateDT >= mFrom && d.CreateDT <= mTo
select (d);
and
private bool TagsContain(string terms, string val)
{
string[] tags = terms.ToLower().Split(';');
return tags.Contains(val.ToLower());
}
but it crashes with not supported error. I think it's because I'm using a custom function TagsContain. How can I do that function in linq without custom stuff?
Thanks

Id TagsContain isn't supported by EF and have an underlying SQL function, it will crash. That's exactly what is happening here.
This however, should work:
from d in db.v_Report_CompanySearches
orderby d.InquiryLogID descending
where (mPersonName == null || d.AccountName.ToLower() == mPersonName || d.PersonName.ToLower() == mPersonName) &&
(mCompanyName == null || d.CompanySearchTerm.Contains(mCompanyName)) &&
d.CreateDT >= mFrom && d.CreateDT <= mTo
select (d);

Provider not able convert your custom function the sql. And I afraid split is one of the functions which not supported for generating sql.
You can use it without .Split
var query =
db.v_Report_CompanySearches
.Where(report => report.CreateDT >= from)
.Where(report => report.CreateDT <= to);
if (String.IsNullOrEmpty(personName) == false)
{
query = query.Where(report => report.AccountName.ToLower() == personName ||
report.PersonName.ToLower() == personName);
}
if (String.IsNullOrEmpty(companyName) == false)
{
query = query.Where(report => report.CompanySearchTerm.StartsWith($"{companyName};") ||
report.CompanySearchTerm.Contains($";{companyName};")) ||
report.CompanySearchTerm.EndsWith($";{companyName}"))
}
var result = query.OrderByDescending(report => report.InquiryLogID).ToList();

What Fabio said is right. Split function of c# can not be converted into SQL query. So, you have one way here
Get all the values from DB into C# List object and then apply the split filter over it.
var myListObject = (from d in db.v_Report_CompanySearches
orderby d.InquiryLogID descending
where (mPersonName == null || d.AccountName.ToLower() == mPersonName || d.PersonName.ToLower() == mPersonName) &&
d.CreateDT >= mFrom && d.CreateDT <= mTo
select (d)).ToList();
Then
var afterFilterObject = myListObject.Where(d => (d.mCompanyName == null || TagsContain(d.CompanySearchTerm, mCompanyName))).ToList();
Method to be called
private bool TagsContain(string terms, string val)
{
string[] tags = terms.ToLower().Split(';');
return tags.Contains(val.ToLower());
}

How to recursively call Where clause in Linq or SQL

Let's say I have the following filter parameters:
Type="Student"
School = "High"
ReferenceID = "123abc"
PaymentOnFile= "Y"
Now, I need to find 1st student based on these 4 parameters. If no students are found then I need to find them based on the 3 parameters, if no students are found then use 2 parameters, etc.
Here's my current code:
var Student = db.Students.Where(x=> x.School == School && x.Type == Type && x.ReferenceID == ReferenceID && x.PaymentOnFile == PaymentOnFile).FirstOrDefault();
if (Student == null)
{
Student = db.Students.Where(x=> x.School == School && x.Type == Type && x.ReferenceID == ReferenceID).FirstOrDefault();
}
if (Student == null)
{
Student = db.Students.Where(x=> x.School == School && x.Type == Type).FirstOrDefault();
}
if (Student == null)
{
Student = db.Students.Where(x=> x.School == School).FirstOrDefault();
}
return Student;
This works but it is not very efficient and ugly. What is a better way to do this? Maybe using expression trees or something else but I cannot figure it out.
SQL also works!

I think something like this would work:
var student = db.Students
.Where(x => x.School == school)
.OrderBy(x => (x.Type == type) ? 0 : 1)
.ThenBy(x => (x.ReferenceID == referenceId) ? 0 : 1)
.ThenBy(x => (x.PaymentOnFile == paymentOnFile) ? 0 : 1)
.FirstOrDefault();

This dynamic solution will perform exactly your recursive logic and will work at case of Linq and EF. You can add another conditions(to predicates, order matters), solution(for loop) will remain the same.
var predicates = new List<Expression<Func<Student, bool>>>
{
x => x.School == "High",
x => x.Type == "Student",
x => x.ReferenceID == "123abc",
x => x.PaymentOnFile == "Y",
};
Student student = null;
for(var i = 0; i < predicates.Count; i++)
{
var query = db.Students.AsQueryable();
for (var j = 0; j < predicates.Count - i; j++)
query = query.Where(predicates[j]);
if ((student = query.FirstOrDefault()) != null)
break;
}

i guess if you could apply this query logic which can help you better
SELECT TOP 1
*
FROM Student AS S
ORDER BY CASE
WHEN S.School = #School AND S.[Type] = #Type AND S.ReferenceID = #ReferenceID AND S.PaymentOnFile = #PaymentOnFile THEN
1
WHEN S.School = #School AND S.[Type] = #Type AND S.ReferenceID = #ReferenceID THEN
2
WHEN S.School = #School AND S.[Type] = #Type THEN
3
WHEN S.School = #School THEN
4
END ASC

Comma separated List in linq select

I have Table HR_Travel(TravelID, TravelCode....) and HR_TravelDocuments(TravelDocID, TravelID, DocUrl)
FromDate = FromDate.AddDays(1);
ToDate = ToDate.AddDays(1);
List<dynamic> Lst = new List<dynamic>();
var queryTravelDetails = from t in db.HR_TravelDetails
where ((t.StatusDate >= FromDate && t.StatusDate <= ToDate)
&& (t.EmpID == EmpID || EmpID == 0) && (t.TravelStatus == TravelStatus || TravelStatus == "All"))
orderby t.StatusDate descending
select new
{
TravelID = t.TravelID,
TravelSubID = db.HR_TravelDetails.Where(i => i.TravelID == 0).FirstOrDefault().TravelID == null ? 0 : db.HR_TravelDetails.Where(i => i.TravelID == 0).FirstOrDefault().TravelID,
t.TravelCode,
t.EmpID,
EmpName = db.EE_Employee.Where(i => i.EmpID == t.EmpID).FirstOrDefault().EmpName,
t.CellNo,
t.BoardingForm,
t.DestinationTO,
t.JournyDate,
t.Purpose,
t.Organization,
t.TravelStatus,
DocUrl = DocUrl = string.Join(",",( db.HR_TravelDocuments.Where(i => i.TravelID == t.TravelID && i.TravelSubID == 0).Select(i => i.DocUrl).ToList()))
};
foreach (var element in queryTravelDetails)
{
Lst.Add(element);
}
Gives the following error:
LINQ to Entities does not recognize the method 'System.String Join[String](System.String, System.Collections.Generic.IEnumerable`1[System.String])' method, and this method cannot be translated into a store expression.

The Join() method can't be used in LINQ expressions, because it cannot translate from CLR to T-SQL. Another example is that you can't use:
var itemCount = db.Table.Count(p => p.Something == SomeFunction(someVariable));
You should move the method call outside the LINQ statement:
var anotherVariable = SomeFunction(someVariable);
var itemCount = db.Table.Count(p => p.Something == anotherVariable);
I hope I explained in a good way.
EDIT: As seen in the comments before, you can also use ToArray() and when the data is loaded locally you can use functions in statements freely.