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How do you reuse mapping functions on Nested entities in Entity Framework?

I have seen multiple questions that are similar to this one but I think my case is slightly different. I'm using EF6 to query the database and I'm using data projection for better queries.
Given that performance is very important on this project I have to make sure to just read the actual fields that I will use so I have very similar queries that are different for just a few fields as I have done this I have noticed repetition of the code so I'm been thinking on how to reuse code this is currently what I Have:
public static IEnumerable<FundWithReturns> GetSimpleFunds(this DbSet<Fund> funds, IEnumerable<int> fundsId)
{
IQueryable<Fund> query = GetFundsQuery(funds, fundsId);
var results = query
.Select(f => new FundWithReturns
{
Category = f.Category,
ExpenseRatio = f.ExpenseRatio,
FundId = f.FundId,
Name = f.Name,
LatestPrice = f.LatestPrice,
DailyReturns = f.FundDailyReturns
.Where(dr => dr.AdjustedValue != null)
.OrderByDescending(dr => dr.CloseDate)
.Select(dr => new DailyReturnPrice
{
CloseDate = dr.CloseDate,
Value = dr.AdjustedValue.Value,
}),
Returns = f.Returns.Select(r => new ReturnValues
{
Daily = r.AdjDaily,
FiveYear = r.AdjFiveYear,
MTD = r.AdjMTD,
OneYear = r.AdjOneYear,
QTD = r.AdjQTD,
SixMonth = r.AdjSixMonth,
ThreeYear = r.AdjThreeYear,
YTD = r.AdjYTD
}).FirstOrDefault()
})
.ToList();
foreach (var result in results)
{
result.DailyReturns = result.DailyReturns.ConvertClosingPricesToDailyReturns();
}
return results;
}
public static IEnumerable<FundListVm> GetFundListVm(this DbSet<Fund> funds, string type)
{
return funds
.Where(f => f.StatusCode == MetisDataObjectStatusCodes.ACTIVE
&& f.Type == type)
.Select(f => new FundListVm
{
Category = f.Category,
Name = f.Name,
Symbol = f.Symbol,
Yield = f.Yield,
ExpenseRatio = f.ExpenseRatio,
LatestDate = f.LatestDate,
Returns = f.Returns.Select(r => new ReturnValues
{
Daily = r.AdjDaily,
FiveYear = r.AdjFiveYear,
MTD = r.AdjMTD,
OneYear = r.AdjOneYear,
QTD = r.AdjQTD,
SixMonth = r.AdjSixMonth,
ThreeYear = r.AdjThreeYear,
YTD = r.AdjYTD
}).FirstOrDefault()
}).OrderBy(f=>f.Symbol).Take(30).ToList();
}
I'm trying to reuse the part where I map the f.Returns so I tried created a Func<> like the following:
private static Func<Return, ReturnValues> MapToReturnValues = r => new ReturnValues
{
Daily = r.AdjDaily,
FiveYear = r.AdjFiveYear,
MTD = r.AdjMTD,
OneYear = r.AdjOneYear,
QTD = r.AdjQTD,
SixMonth = r.AdjSixMonth,
ThreeYear = r.AdjThreeYear,
YTD = r.AdjYTD
};
and then use like this:
public static IEnumerable<FundListVm> GetFundListVm(this DbSet<Fund> funds, string type)
{
return funds
.Where(f => f.StatusCode == MetisDataObjectStatusCodes.ACTIVE
&& f.Type == type)
.Select(f => new FundListVm
{
Category = f.Category,
Name = f.Name,
Symbol = f.Symbol,
Yield = f.Yield,
ExpenseRatio = f.ExpenseRatio,
LatestDate = f.LatestDate,
Returns = f.Returns.Select(MapToReturnValues).FirstOrDefault()
}).OrderBy(f=>f.Symbol).Take(30).ToList();
}
The compiler is ok with it but at runtime, it crashes and says: Internal .NET Framework Data Provider error 1025
I tried to convert the Func into Expression like I read on some questions and then using compile() but It didn't work using AsEnumerable is also not an option because It will query all the fields first which is what I want to avoid.
Am I trying something not possible?
Thank you for your time.

It definitely needs to be Expression<Func<...>>. But instead of using Compile() method (not supported), you can resolve the compile time error using the AsQueryable() method which is perfectly supported (in EF6, the trick doesn't work in current EF Core).
Given the modified definition
private static Expression<Func<Return, ReturnValues>> MapToReturnValues =
r => new ReturnValues { ... };
the sample usage would be
Returns = f.Returns.AsQueryable().Select(MapToReturnValues).FirstOrDefault()

Linq where clause using filter object

I have a piece of Linq that queries an EntityFramework context in my web controller and returns the result, as follows:
[HttpGet]
public IActionResult GetRoutingRules()
{
var query = (from rr in _context.RoutingRules
join dest in _context.RoutingZones on rr.DestinationZoneId equals dest.ZoneId
join origin in _context.RoutingZones on rr.OriginZoneId equals origin.ZoneId
join hub in _context.RoutingHub on rr.HubId equals hub.HubId
select new RoutingRulesDto(rr) { DestinationZoneName = dest.ZoneName, OriginZoneName = origin.ZoneName, HubName = hub.HubName });
return Ok(query);
}
I want a new method that will take a "filter" object, where I can narrow down the results of the above. My filter object looks like this:
public class RoutingSearchFilterDto
{
public int BrandId { get; set; }
public int? ServiceType { get; set; }
public long? OriginZoneId { get; set; }
public long? DestinationZoneId { get; set; }
public int? RuleRanking { get; set; }
public bool? IsRuleActive { get; set; }
}
The minimum info that needs to be set in this class is BrandId. All other properties are options in the filter.
I need to write a new controller method that will utilise this, something like:
[HttpPost("filtered")]
public IActionResult GetFilteredRoutingRules([FromBody] RoutingSearchFilterDto filter)
{
...
}
How do I linq query on properties that could potentially be null? Essentially, a dynamic query depending on the properties set in the filter object.
NOTE: I want this to affect the select statement that the EF runs, not just let EF get all the data, then filter the data set - the point of this is to make the db call more efficient.
Filter object might be sent where BrandId = 1, IsRuleActive = 1. Equally, it could be BrandId = 1, ServiceType = 3 (and therefore IsRuleActive is null so shouldn't be in the linq where clause).
I've tried this:
var param = (Expression.Parameter(typeof(RoutingRules), "rr"));
Expression combinedExpr = null;
if (filter.BrandId != null)
{
var exp = Expression.Equal(Expression.Property(param, "BrandId"), Expression.Constant(filter.BrandId));
combinedExpr = exp;
}
if (filter.DestinationZoneId != null)
{
var exp = Expression.Equal(Expression.Property(param, "DestinationZoneId"), Expression.Constant(filter.DestinationZoneId));
combinedExpr = (combinedExpr == null ? exp : Expression.AndAlso(combinedExpr, exp));
}
if (filter.OriginZoneId != null)
{
var exp = Expression.Equal(Expression.Property(param, "OriginZoneId"), Expression.Constant(filter.OriginZoneId));
combinedExpr = (combinedExpr == null ? exp : Expression.AndAlso(combinedExpr, exp));
}
if (filter.EshopServiceType != null)
{
var exp = Expression.Equal(Expression.Property(param, "EshopServiceType"), Expression.Constant(filter.EshopServiceType));
combinedExpr = (combinedExpr == null ? exp : Expression.AndAlso(combinedExpr, exp));
}
if (filter.IsRuleActive != null)
{
var exp = Expression.Equal(Expression.Property(param, "IsRuleActive"), Expression.Constant(filter.IsRuleActive, typeof(bool?)));
combinedExpr = (combinedExpr == null ? exp : Expression.AndAlso(combinedExpr, exp));
}
if (filter.RuleRanking != null)
{
var exp = Expression.Equal(Expression.Property(param, "RuleRanking"), Expression.Constant(filter.RuleRanking));
combinedExpr = (combinedExpr == null ? exp : Expression.AndAlso(combinedExpr, exp));
}
if (combinedExpr == null)
combinedExpr = Expression.Default(typeof(bool));
var compiled = Expression.Lambda<Func<RoutingRules, bool>>(combinedExpr, param).Compile();
var results = (from rr in _context.RoutingRules.Where(compiled)
join dest in _context.RoutingZones on rr.DestinationZoneId equals dest.ZoneId
join origin in _context.RoutingZones on rr.OriginZoneId equals origin.ZoneId
join hub in _context.RoutingHub on rr.HubId equals hub.HubId
where rr.BrandId == 21
select new RoutingRulesDto(rr) { DestinationZoneName = dest.ZoneName, OriginZoneName = origin.ZoneName, HubName = hub.HubName });
But the Where clause isn't applied to the generated Sql, it seems to pull back all records, then apply the where in memory, which isn't what I need.
Thanks in advance for any pointers!!

You can build an expression tree for this, but have you considered:
IQueryable<...> query = ...;
if (routingSearchFilter.ServiceType != null)
query = query.Where(e => e.ServiceType == routingSearchFilter.ServiceType);
if (...)
query = query.Where(....);
The EF engine is smart enough to combine the Where clauses (with AND of course).
Edit:
It wasn't clear if you wanted to filter on the joined result or only on the first table. In that case it would continue like
var result = (from rr in query
join dest in _context.RoutingZones on rr.DestinationZoneId equals dest.ZoneId
join ...
select new RoutingRulesDto(rr) .... ).ToSometing();
But I'm a little wary about that RoutingRulesDto(rr) constructor parameter.

If you use the fluent API for LINQ, you can conditionally add Where clauses.
var query = _content.RoutingRules.Where(r => r.BrandId == filter.BrandId);
if (filter.OriginZoneId != null) {
query = query.Where(r => r.OriginZoneId == filter.OriginZoneId);
}
if (filter.EshopServiceType != null) {
query = query.Where(r => r.EshopServiceType == filter.EshopServiceType);
}
// etc...
var result = query.ToArray();

Just to have my final solution in black and white, here's what I had in the end:
[HttpPost("filtered")]
public IActionResult GetFilteredRoutingRules([FromBody] RoutingSearchFilterDto filter)
{
// Query to be build on the routing rules table.
IQueryable<RoutingRules> query = _context.RoutingRules;
// Populate the linked foreign key entities.
query.Include(x => x.Hub).Include(y => y.DestinationZone).Include(z => z.OriginZone);
// Build dynamic where statements.
if (filter.BrandId != null)
query = query.Where(r => r.BrandId == filter.BrandId);
if (filter.OriginZoneId != null)
query = query.Where(r => r.OriginZoneId == filter.OriginZoneId);
if (filter.DestinationZoneId != null)
query = query.Where(r => r.DestinationZoneId == filter.DestinationZoneId);
if (filter.IsRuleActive != null)
query = query.Where(r => r.IsRuleActive == filter.IsRuleActive);
if (filter.RuleRanking != null)
query = query.Where(r => r.RuleRanking == filter.RuleRanking);
// If you want to add paging:
query = query.Skip(filter.PageSize * filter.PageNumber).Take(filter.PageSize);
// Perform select on the table and map the results.
var result = query.Select(r => new RoutingRulesDto
{
RoutingRuleId = r.RoutingRuleId,
BrandId = r.BrandId,
LastMileCarrierCode = r.LastMileCarrierCode,
CashOnDelivery = r.CashOnDelivery,
CreationTime = r.CreationTime,
CurrencyCode = r.CurrencyCode,
CurrencyDescription = Enum.Parse(typeof(Enumerations.CurrencyCode), r.CurrencyCode),
DestinationZoneId = r.DestinationZoneId,
EddFromDay = r.EddFromDay,
EddToDay = r.EddToDay,
ServiceType = r.ServiceType,
ServiceTypeName = Enum.Parse(typeof(Enumerations.ServiceType), r.EshopServiceType),
IsPickUpAvailable = r.IsPickUpAvailable,
LastUpdateTime = r.LastUpdateTime,
LastUpdateUser = r.LastUpdateUser,
OriginZoneId = r.OriginZoneId,
RuleRanking = r.RuleRanking,
SignOnDelivery = r.SignOnDelivery,
TermsOfDelivery = r.TermsOfDelivery,
TermsOfDeliveryName = Enum.Parse(typeof(Enumerations.TermsOfDelivery), r.TermsOfDelivery),
ValueOfGoods = r.ValueOfGoods,
WeightLowerLimit = r.WeightLowerLimit,
WeightUpperLimit = r.WeightUpperLimit,
FirstMileCarrierCode = r.FirstMileCarrierCode,
HubId = r.HubId,
IsInsuranceAvailable = r.IsInsuranceAvailable,
IsRuleActive = r.IsRuleActive,
HubName = r.Hub.HubName,
DestinationZoneName = r.DestinationZone.ZoneName,
OriginZoneName = r.OriginZone.ZoneName,
});
// The SQL produced includes the joins and where clauses as well as only
// selecting the column names that are required in the flattened return object.
return Ok(result);
}
Thanks for the help guys!

Search form has an Enum dropdown field whose value may be null (none selected) once it reaches my lambda Linq query

Basically, if the user selected no option from the dropdown combo, I want it to be left out from my Linq query that looks something like this:
// this is how I manage the form post data, please
// propose a better way if you know one
Dictionary<string, string> formdata = new Dictionary<string, string>();
foreach(string key in Request.Form.AllKeys)
{
formdata.Add(key, Request.Form[key]);
}
// getting the title
string title = "";
formdata.TryGetValue("postedTitle", out title);
// getting the level
string levelString = "";
formdata.TryGetValue("postedLevel", out levelString );
int level = -1;
if(levelString != "")
{
Int32.TryParse(levelString , out level);
}
var model = new FooIndexVM
{
Foos = _ctx.SomeDbSet.Where(w => w.Title.Contains(title) && w.Level == (Level?)level.Value).Select(x => new FooBarRow
{
FooBarId = x.Id,
....
Since I'm getting either 0 or -1 for the level -- I need a way to gracefully leave the Enum part from the query completely. I will also later add some additional fields similar to this one (may be unselected) so the solution will also work for those, I guess.

You can chain Where commands so this line:
Foos = _ctx.SomeDbSet.Where(w => w.Title.Contains(title) && w.Level == (Level?)level.Value).Select(x => new FooBarRow
{
FooBarId = x.Id,
....
Could be rewritten to be this without changing its behaviour (multiple Wheres effectively become combined with &&s):
Foos = _ctx.SomeDbSet.Where(w => w.Title.Contains(title)).Where(w => w.Level == (Level?)level.Value).Select(x => new FooBarRow
{
FooBarId = x.Id,
....
This then means that you can add some logic around whether to apply the second Where or not like this, for example:
var query = _ctx.SomeDbSet.Where(w => w.Title.Contains(title));
if (level != -1)
{
query = query.Where(w => w.Level == (Level?)level.Value)
}
Foos = query.Select(x => new FooBarRow
{
FooBarId = x.Id,

Linq to SQL - Ignore search parameters that are null or zero

I have a search form where the user can enter one to many parameters (Data, Status, Type, ID, Summary, Description) and leave the rest blank.
Here's my Linq to SQL code for my basic search. Is there a way to check each parameter within the Linq for zero, null or empty string?
List<RequestStatusModel> objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where r.CustomerID == 31
select (new RequestStatusModel
{
RequestID = r.RequestID,
RequestTitle = r.RequestTitle,
DateAdded = r.DateAdded.ToString(),
DateChanged = r.DateChanged.ToString(),
RequestStatusID = r.StatusID
});
Thank you!

If it doesn't have to be in your linq statement you could just do it with classic if statements.
List<RequestStatusModel> objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where r.CustomerID == 31
select (new RequestStatusModel
{
//...
});
if(data != null) //Replace with additional checks, if neccessary
{
query = query.where(x=> ...);
}
if(status != null)
{
query = query.where(x => ...)
}

If you want to only filter if certain criteria is passed, you should do something like this
var objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where r.CustomerID == 31
if (String.IsNullOrEmpty(r.RequestID))
objRequestStatus = objRequestStatus.Where(x => x.RequestID == r.RequestID);
if (String.IsNullOrEmpty(r.RequestTitle))
objRequestStatus = objRequestStatus.Where(x => x.RequestTitle == r.RequestTitle);
//you other filters here
This sets up the expression to what you want based on which requests are passed

If you want to avoid all those ifs, you could do
List<RequestStatusModel> objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where (r.CustomerID == 31) &&
(!String.IsNullOrEmpty(id) ? r.RequestID == id : true) &&
(!String.IsNullOrEmpty(status) ? r.StatusID == status : true)
/* And so on */
select (new RequestStatusModel
{
RequestID = r.RequestID,
RequestTitle = r.RequestTitle,
DateAdded = r.DateAdded.ToString(),
DateChanged = r.DateChanged.ToString(),
RequestStatusID = r.StatusID
});

query item using linq and return type in the same statement?

I have the following two lines of code which first returns an item from a query and then creates another item with the values of the first query. i would like to combine these two lines into one statement. Keep in mind that the result of the first query might be null on some occasions.
var x = uow.Profiles.FindByID(profileId).Competitor;
return Json(new Organisation() { Name = x.Name, ID = x.ID, IsClient = x.IsClient, IsDeleted = x.IsDeleted }, JsonRequestBehavior.AllowGet);

Maybe you can add a null check if this is your concern:
var result = uow.Profiles.FindByID(profileId);
if(result != null)
{
var competitor = result.Competitor;
return Json(new Organisation() { Name = competitor.Name, ID = competitor.ID, IsClient = competitor.IsClient, IsDeleted = competitor.IsDeleted }, JsonRequestBehavior.AllowGet);
}
return null; // or whatever you can default to
Not sure exactly what the problem is and how LINQ could help (you don't necessary have to use it), just make sure your code is readable.

Edit: finally using IEnumerable (I assume Profiles is one)
ouw.Profiles.Single(p => p.Id == profileId).Select
(p => Json(
new Organisation()
{
Name = p.Competitor.Name,
ID = p.Competitor.ID,
IsClient = p.Competitor.IsClient,
IsDeleted = p.Competitor.IsDeleted
},
JsonRequestBehavior.AllowGet)
);