Entity Framework - LINQ selection in POCO generic List property - linq

I'm having some issues setting a generic list property of a POCO object when from an EF context. For instance I have a very simple object that contains the following:
public class foo
{
public string fullName;
public Entity entity;
public List<SalesEvent> eventList;
}
My code to populate this object from looks something like this:
.Select(x => new foo()
{
fullName = x.vchFirstName + " " + x.vchLastName,
entity = new EntityVo()
{
address1 = x.vchAddress1,
entityId = x.iEntityId,
emailAddress = x.vchEmailAddress,
firstName = x.vchFirstName,
lastName = x.vchLastName,
city = x.vchCity,
state = x.chState,
workNumber = x.vchWorkNumber,
mobileNumber = x.vchMobileNumber,
siteId = x.iSiteId
}
eventList = _context.Events
.Where(e => e.iEntityId == x.iEntityId
&& e.iStatusId >= eventStatusMin
&& e.iStatusId <= eventStatusMax)
.Select(e => new List<SalesEventMatchVo>
{
new SalesEventMatchVo()
{
vehicleName = _context.Quotes.Select(q=>q).Where(q=>q.iEventId == e.iEventId).FirstOrDefault().vchMake + " " + _context.Quotes.Select(q=>q).Where(q=>q.iEventId == e.iEventId).FirstOrDefault().vchModel,
eventId = e.iEventId,
salesPerson = e.chAssignedTo,
eventStatusDesc=_context.RefDefinitions.Select(r=>r).Where(r=>r.iParameterId==e.iStatusId).FirstOrDefault().vchParameterDesc,
eventStatusId =(int)e.iStatusId,
eventSourceDesc=_context.RefDefinitions.Select(r=>r).Where(r=>r.iParameterId==e.iSourceId).FirstOrDefault().vchParameterDesc,
createDate = e.dtInsertDate
}
}).FirstOrDefault()
}).ToArray();
This issue I'm having is that I'm unable to populate the eventList property with all of the events, it's only grabbing the first record(which makes sense looking at the code). I just cant seem to figure out to populate a the entire list.

Is there a reason simply removing the FirstOrDefault at the end isn't the solution here? I feel like I might be misunderstanding something.
EDIT:
I think I see what you are trying to do. The issue is that you are creating a list in the select statement, when the select statement works only over one thing at a time. It is basically mapping an input type to a new output type.
Try something like this instead:
eventList = _context.Events.Where(e => e.iEntityId == x.iEntityId && //FILTER EVENTS
e.iStatusId >= eventStatusMin &&
e.iStatusId <= eventStatusMax)
.Select(e => new SalesEventMatchVo() //MAP TO SALESEVENT
{
vehicleName = _context.Quotes.Select(q=>q).Where(q=>q.iEventId == e.iEventId).FirstOrDefault().vchMake + " " + _context.Quotes.Select(q=>q).Where(q=>q.iEventId == e.iEventId).FirstOrDefault().vchModel,
eventId = e.iEventId,
salesPerson = e.chAssignedTo,
eventStatusDesc=_context.RefDefinitions.Select(r=>r).Where(r=>r.iParameterId==e.iStatusId).FirstOrDefault().vchParameterDesc,
eventStatusId =(int)e.iStatusId,
eventSourceDesc=_context.RefDefinitions.Select(r=>r).Where(r=>r.iParameterId==e.iSourceId).FirstOrDefault().vchParameterDesc,
createDate = e.dtInsertDate
})
.ToList() //CONVERT TO LIST
As a side note, unless you actually need a List for some reason, I would store foo.eventList as IEnumerable<SalesEvent> instead. This allows you to skip the List conversion at the end, and in some scenarios enables neat tricks like delayed and/or partial execution.
Also, I'm not sure what the point of your .Select(q=>q) statements are in several lines of the SalesEventMatchVo initializer, but I'm pretty sure you can chop them out. If nothing else, you should Select after Where, as Where can reduce the work performed by all following statements.

Related

Automapper with linq how?

Ok, I'm really struggling with finding a good example of what I need to do. So, I'll ask here.
Let's say I have a entity class (EF) named Customer and a corresponding view-model class named CustomerViewModel.
Using AutoMapper, I have created the following mappings:
Mapper.CreateMap<CustomerViewModel, Customer>();
Mapper.CreateMap<Customer, CustomerViewModel>();
How would I modify the following code to make use of this mapping?
public static List<CustomerViewModel> GetCustomers()
{
using (var context = new GCSBaseEntities())
{
var query = from c in context.Customers
select new CustomerViewModel
{
CompanyName = c.CompanyName,
Id = c.Id,
EmailAddress = c.EmailAddress,
FirstName = c.FirstName,
LastName = c.LastName,
MiddleName = c.MiddleName,
ModifiedDate = c.ModifiedDate,
Phone = c.Phone,
SalesPerson = c.SalesPerson,
Suffix = c.Suffix,
Title = c.Title,
FullName = c.FirstName + " " + c.LastName
};
return query.ToList();
}
}
Thanks in advance.
When you register your mappings, you must provide any complex mapping operations that have to occur. In your case, I believe all your properties match up, except for FullName = c.FirstName + " " + c.LastName. Here's how your Customer-to-CustomerViewModel mapping should look:
Mapper.CreateMap<Customer, CustomerViewModel>()
.ForMember(custVm => custVm.FullName,
mapper => mapper.MapFrom(cust => cust.FirstName + " " + cust.LastName));
You'll have to figure out how to shove the FullName prop from the ViewModel back into the FirstName & LastName fields on the EF class, though. But when you decide how to implement it, follow the pattern from above for the other mapping.
Your query can now be MUUUCH smaller:
using (var context = new GCSBaseEntities())
{
return from c in context.Customers
select Mapper.Map<CustomerViewModel>(c);
}
Figured it out. In order to avoid the aforementioned error, you have to Add the call the .AsEnumerable() after Customers like so:
return from c in context.Customers.AsEnumerable()
select Mapper.Map<CustomerViewModel>(c);
I got this from this thread: LINQ and AutoMapper

generic method to search for an LINQ entity based on its type

partial void UpdateDenomLimit(DenomLimit instance)
{
var oldData = DataClassesDataContext.DenomLimits.Where(b => b.ID == instance.ID).First();
//Code that logs the audit when instance and oldData is passed to it
LogAudit(oldData, instance);
//Code that updates the instance
this.ExecuteDynamicUpdate(instance);
}
Above is a method for updating an instance of DenomLimit in the database.
I am logging an audit of what changes are done to the entity. For that I get the previous state of the instance by the following code and it works fine:
var oldData = DataClassesDataContext.DenomLimits.Where(b => b.ID == instance.ID).First();
now I need a generic LINQ query which can fetch the oldData when three parameters are passed to it:
1. an instance of any type
2. A primary key column name
3. A value of primary key column for the passed instance.
...so that I can keep that code in the LogAudit and then do not need to fetch in every function.
A LINQ query which will possibly look like:
var oldData = DataClassesDataContext.GetTable<instance>().Where("b => b." + colName + " == #0", new object[] { id }).First();
The full namespace is used here to indicate the namespace that it came from to make it easier to incorporate into your code.
public T GetFirstOrDefault<T>(System.Linq.Expressions.Expression<Func<T, bool>> func) where T : class
{
DataClassesDataContext.ObjectContext.CreateObjectSet<T>().FirstOrDefault(func);
// For EF 4.1 Code First
//return (ctx as System.Data.Entity.Infrastructure.IObjectContextAdapter).ObjectContext.CreateObjectSet<T>().FirstOrDefault(func);
// or
//return ctx.Set<T>().FirstOrDefault(func);
}
In this case using an Expression of a Func allows EF to figure out what data you are looking for.
Here is an example of how it would be used:
var a1 = GetFirstOrDefault<DenomLimits>(p => p.ID == oldData.ID);
var a2 = GetFirstOrDefault<DenomLimits>(p => p.OtherID == 5);

IN and NOT IN with Linq to Entities (EF4.0)

This has been ruining my life for a few days now, time to ask...
I am using Entity Framework 4.0 for my app.
A Location (such as a house or office) has one or more facilities (like a bathroom, bedroom, snooker table etc..)
I want to display a checkbox list on the location page, with a checkbox list of facilities, with the ones checked that the location currently has.
My View Model for the facilities goes like this...
public class FacilityViewItem
{
public int Id { get; set; }
public string Name { get; set; }
public bool Checked { get; set; }
}
So when im passing the Location View Model to the UI, i want to pass a List<T> of facilities where T is of type FacilityViewItem.
To get the facilities that the location already has is simple - i make a query using Location.Facilities which returns an EntityCollection where T is of type Facility. This is because Facilities is a navigation property....
var facs = from f in location.Facilities
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name,
Checked = true
};
So here is where my problem lies - i want the rest of the facilities, the ones that the Location does not have.
I have tried using Except() and Any() and Contains() but i get the same error.
Examples of queries that do not work...
var restOfFacilities = from f in ctx.Facilities
where !hasFacilities.Contains(f)
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name
};
var restOfFacilities = ctx.Facilities.Except(facilitiesThatLocationHas);
var notFacs = from e in ctx.Facilities
where !hasFacilities.Any(m => m.FacilityId == e.FacilityId)
select new FacilityViewItem()
{
Id = e.FacilityId,
Name = e.Name
};
And the error i get with every implementation...
System.NotSupportedException was unhandled
Message=Unable to create a constant value of type 'Chapter2ConsoleApp.Facility'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
What am i overlooking here?
ironically enough i solved it in a matter of hours after i posted the question on here, after days of suffering.
The error is basically saying 'i dont know how to calculate what items are not included by comparing strongly typed objects. Give me a list of Ints or some simple types, and i can take care of it'.
So, first you need to get a list of the primary keys, then use that in the contains clause...
//get the primary key ids...
var hasFacilityIds = from f in hasFacilities
select f.FacilityId;
//now use them in the contains clause...
var restOfFacilities = from f in ctx.Facilities
where !hasFacilityIds.Contains(f.FacilityId)
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name
};
The first query seems fine, but you need to compare the Ids:
var restOfFacilities = from f in ctx.Facilities
where !facs.Select(fac => fac.Id).Contains(f.Id)
select f;
I wanna see what's hasFacilities, anyway, as L2E shows, "Only primitive types ('such as Int32, String, and Guid') are supported in this context", so I suppose you must retrieve first the data and put into a collection of FacilityViewItem.
var restOfFacilities = ctx
.Facilities
.Where(f => !hasFacilities.Contains(f))
.Select(f => new { f.FacilityId, f.Name })
.ToList()
.Select(f => new FacilityViewItem {
Id = f.FacilityId,
Name = f.Name
});
var notFacs = ctx
.Facilities
.Where(e => !hasFacilities.Any(m => m.FacilityId == e.FacilityId))
.Select(e => new { e.FacilityId, e.Name })
.ToList()
.Select(e => new FacilityViewItem {
Id = e.FacilityId,
Name = e.Name
});
hope it helps

Only primitive types ('such as Int32, String, and Guid') are supported in this context when I try updating my viewmodel

I am having some trouble with a linq query I am trying to write.
I am trying to use the repository pattern without to much luck. Basically I have a list of transactions and a 2nd list which contains the description field that maps against a field in my case StoreItemID
public static IList<TransactionViewModel> All()
{
var result = (IList<TransactionViewModel>)HttpContext.Current.Session["Transactions"];
if (result == null)
{
var rewardTypes = BusinessItemRepository.GetItemTypes(StoreID);
HttpContext.Current.Session["Transactions"] =
result =
(from item in new MyEntities().TransactionEntries
select new TransactionViewModel()
{
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
}).ToList();
}
return result;
}
public static List<BusinessItemViewModel>GetItemTypes(int storeID)
{
var result = (List<BusinessItemViewModel>)HttpContext.Current.Session["ItemTypes"];
if (result == null)
{
HttpContext.Current.Session["ItemTypes"] = result =
(from items in new MyEntities().StoreItems
where items.IsDeleted == false && items.StoreID == storeID
select new BusinessItemViewModel()
{
ItemDescription = items.Description,
StoreID = items.StoreID,
StoreItemID = items.StoreItemID
}).ToList();
}
return result;
However I get this error
Unable to create a constant value of type 'MyMVC.ViewModels.BusinessItemViewModel'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
I know its this line of code as if I comment it out it works ok
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
How can I map ItemDescription against my list of itemTypes?
Any help would be great :)
This line has a problem:
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription,
Since you are using FirstOrDefault you will get null as default value for a reference type if there is no item that satifies the condition, then you'd get an exception when trying to access ItemDescription - either use First() if there always will be at least one match or check and define a default property value for ItemDescription to use if there is none:
ItemDescription = itemTypes.Any(r=>r.StoreItemID==item.StoreItemID)
? itemTypes.First(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription
: "My Default",
If itemTypes is IEnumerable then it can't be used in your query (which is what the error message is telling you), because the query provider doesn't know what to do with it. So assuming the that itemTypes is based on a table in the same db as TransactionEntities, then you can use a join to achieve the same goal:
using (var entities = new MyEntities())
{
HttpContext.Current.Session["Transactions"] = result =
(from item in new entities.TransactionEntries
join itemType in entities.ItemTypes on item.StoreItemID equals itemType.StoreItemID
select new TransactionViewModel()
{
ItemDescription = itemType.ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
CustomerName = rewards.CardID//TODO: Get customer name
}).ToList();
}
I don't know the structure of your database, but hopefully you get the idea.
I had this error due a nullable integer in my LINQ query.
Adding a check within my query it solved my problem.
query with problem:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.Equals(y.OBJ_ID));
query with problem solved:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.HasValue && s.Obj_Id.Value.Equals(y.OBJ_ID));

Extracting text from an IEnumerable<T>

I have a IEnumerable<T> collection with Name, FullName and Address.
The Address looks like this:
Street1=54, Street2=redfer street, Pin=324234
Street1=54, Street2=fdgdgdfg street, Pin=45654
Street1=55, Street2=tryry street, Pin=65464
I want to loop through this collection and print only those Names, FullNames whose Street1=54
How can i do it in LINQ?
Ok I was able to do this to extract Street1 of the Address
coll.Address.Split(",".ToCharArray())[0]returns me Street1=54 .
Now how do I add this to the condition and print only those Name, FullName whose Street1=54
Based on your update, you can adapt Jared Par's code this way:
var result = collection.Where(x => x.Address.Contains("Street1=54"));
foreach ( var cur in result ) {
Console.WriteLine(string.Format("{0}, {1}", cur.Name, cur.FullName));
}
If you want to be able to plug in your Street1 value with a variable, then do this:
var street1 = "54";
var result = collection.Where(x => x.Address.Contains("Street1=" + street1 ));
foreach ( var cur in result ) {
Console.WriteLine(string.Format("{0}, {1}", cur.Name, cur.FullName));
}
BTW, you really should update your question or add a comment to a specific answer rather than adding a new answer that isn't.
Try this
var result = collection.Where(x => x.Address.Street1==54);
foreach ( var cur in result ) {
Console.WriteLine(var.Name);
}
Select the correct list of :
IList<T> matches = myListOfEnumerables.Where(m => m.Street1 == 54).ToList();
Then loop and print.
Actually the record looks like this:
{Name="Jan" FullName="Kathy Jan" Address="Street1=54, Street2=redfer street, Pin=324234"}
I have to loop through this collection and print only those Names, FullNames whose Street1=54
If the updated information is accurate, you should change the way you store the data.
It looks like you've packed the address information into a string. Why not store it as an object. In fact, why not just as more fields in the same object as the Name and FullName? (and why duplicate the first-name information?)
public class Person
{
public string FirstName, LastName, Street1, Street2, Pin;
}
IEnumerable<Person> persons = GetAllPersonsSomehow();
foreach (Person person in persons.Where(p => p.Street1 == "54"))
Console.WriteLine(person.LastName + ", " + person.FirstName);
Assuming you have to keep the address information in a string, you need a parser for it.
public static IDictionary<string, string> GetAddressFields(string address)
{
return address.Split(',').ToDictionary(
s => s.Substring(0, s.IndexOf('=')).Trim(),
s => s.Substring(s.IndexOf('=') + 1).Trim());
}
foreach (Person person in persons.Where(p =>
GetAddressFields(p.Address)["Street1"] == "54"))
Console.WriteLine(person.LastName + ", " + person.FirstName);
So, what you could do is that you could write a generator for parsing the Address field and then enumerating properties of that. This is a fairly common thing in the functional programming world.
To be fair you would want this code to be lazy in that it would only compute a minimal set. I'm gonna suggest some code from the BCL but you can (and probably should) rewrite the same helper methods with generators.
public static IEnumerable<KeyValuePair<string,string>> NameValueSplit( this string s )
{
foreach (var x in s.Split(','))
{
var y = x.Split(new char[] { '=' }, 2, StringSplitOptions.None);
yield return new KeyValuePair<string, string>(y[0].TrimStart(), y[1].TrimEnd());
}
}
With that helper function you can write code like this
var result = collection.Where(x => x.Address
.NameValueSplit().Any(x => x.Key == "Street1" && x.Value == "54"));
foreach ( var item in result )
{
Console.WriteLine(item.Name);
}
Now this code will not run on your SQL Server if you were thinking of that, but you could write a WHERE clause where you would search the Address field for a sub string %Street1=54%. I like lazy evaluation for string operations and think that's a lacking feature in the BCL. That is why I suggested that kind of solution.

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