LINQ to Entities similar code

Question

I have similar LINQ to Entities requests:

ComdataFuelDetailVM model = (from i in db.ComdataFuels where i.ID == id.Value select new ComdataFuelDetailVM() { ID = i.ID, CardNo = i.CardNo, City = i.City, CompanyId = i.CompanyId, DriverId = i.DriverId, DriverName = i.DriverName, EmployeeNo = i.EmployeeNo, Fees = i.Fees, GalPrice = i.GalPrice, NoOfGal = i.NoOfGal, OwnerOp = i.OwnerOp, PayoutRebate = i.PayoutRebate, Rebate = i.Rebate, State = i.State, TotalCost = i.TotalCost, TransDate = i.TransDate, TransTime = i.TransTime, TruckNo = i.TruckNo, TruckStopCode = i.TruckStopCode, TruckStopInvoiceNo = i.TruckStopInvoiceNo, TruckStopName = i.TruckStopName, UnitNo = i.UnitNo }).FirstOrDefault(); ComdataFuelDeleteVMmodel = (from i in db.ComdataFuels where i.ID == id.Value select new ComdataFuelDeleteVM() { ID = i.ID, CardNo = i.CardNo, City = i.City, CompanyId = i.CompanyId, DriverId = i.DriverId, DriverName = i.DriverName, EmployeeNo = i.EmployeeNo, Fees = i.Fees, GalPrice = i.GalPrice, NoOfGal = i.NoOfGal, OwnerOp = i.OwnerOp, PayoutRebate = i.PayoutRebate, Rebate = i.Rebate, State = i.State, TotalCost = i.TotalCost, TransDate = i.TransDate, TransTime = i.TransTime, TruckNo = i.TruckNo, TruckStopCode = i.TruckStopCode, TruckStopInvoiceNo = i.TruckStopInvoiceNo, TruckStopName = i.TruckStopName, UnitNo = i.UnitNo }).FirstOrDefault();

etc

ComdataFuelDetailVM and ComdataFuelDeleteVM have the same properties (but used as view models for different views):

public abstract class ComdataFuelAbstractVM { public int ID { get; set; } public int? CompanyId { get; set; } public string TruckNo { get; set; } public int? DriverId { get; set; } [Display(Name = "Date")] [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:MM/dd/yyyy}")] public DateTime TransDate { get; set; } public string TransTime { get; set; } public string DriverName { get; set; } public string UnitNo { get; set; } public string City { get; set; } public string State { get; set; } public string TruckStopCode { get; set; } public string TruckStopName { get; set; } public string TruckStopInvoiceNo { get; set; } public decimal? NoOfGal { get; set; } [DisplayFormat(DataFormatString = "{0:C3}")] public decimal? GalPrice { get; set; } [DisplayFormat(DataFormatString = "{0:c}")] public decimal? TotalCost { get; set; } [DisplayFormat(DataFormatString = "{0:c}")] public decimal? Fees { get; set; } [DisplayFormat(DataFormatString = "{0:c}")] public decimal? Rebate { get; set; } [Display(Name = "Rebate")] [DisplayFormat(DataFormatString = "{0:c}")] public decimal? PayoutRebate { get; set; } public string CardNo { get; set; } public string EmployeeNo { get; set; } public bool? OwnerOp { get; set; } } public class ComdataFuelDetailVM : ComdataFuelAbstractVM { } public class ComdataFuelDeleteVM : ComdataFuelAbstractVM { }

any want to write a method, which returns Expression like this:

private Expression<Func<ComdataFuel, T>> GetPictureExpression<T>() { Expression<Func<ComdataFuel, T>> projection = i => new T() { ID = i.ID, CardNo = i.CardNo, City = i.City, CompanyId = i.CompanyId, DriverId = i.DriverId, DriverName = i.DriverName, EmployeeNo = i.EmployeeNo, Fees = i.Fees, GalPrice = i.GalPrice, NoOfGal = i.NoOfGal, OwnerOp = i.OwnerOp, PayoutRebate = i.PayoutRebate, Rebate = i.Rebate, State = i.State, TotalCost = i.TotalCost, TransDate = i.TransDate, TransTime = i.TransTime, TruckNo = i.TruckNo, TruckStopCode = i.TruckStopCode, TruckStopInvoiceNo = i.TruckStopInvoiceNo, TruckStopName = i.TruckStopName, UnitNo = i.UnitNo }; return projection; }

but I can't create T object...

Antonín Lejsek · Accepted Answer · 2017-06-10 20:06:46Z

private Expression<Func<ComdataFuel, T>> GetPictureExpression<T>() where T: ComdataFuelAbstractVM, new()

to create T you have to add new() constraint

Marcin Zdunek · Accepted Answer · 2017-06-10 19:51:33Z

2

If ComdataFuelDetailVM and ComdataFuelDeleteVM have the same properties then just write common interface or base class for these classes containing all these properties and in your method use this construction:

private Expression<Func<ComdataFuel, T>> GetPictureExpression<T>() where T : ICommonInterface

answered Jun 10, 2017 at 19:51

Marcin Zdunek

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4 Comments

Oleg Sh Over a year ago

It's not a rule. These classes can have different superclasses, but have the same properties... Also, I want to have a flexible solution if classes have a little difference (i.e. one property) etc

Marcin Zdunek Over a year ago

So just use common interface for them, not common superclass. Common interface will contain all properties which are shared by these classes and it will allow to write generic method in way that i have provided

Oleg Sh Over a year ago

Interfaces will increase subclasses and add difficulties to add/remove new properties..

Marcin Zdunek Over a year ago

I don't think that there is another way to do it

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