I use the following code to remove all KlientDoTrasa assigned to trasaOriginal and then create and assign new KlientDoTrasa based on collection: trasaToEdit.Klienci. In my test case assigned KlientDoTrasa and new KlientDoTrasa are the same, so I thought EF4 should not send any query to database, but it sends, first deletes then inserts. Is there a way to limit it?
public void Edit(int trasaId, TrasaEditViewModel trasaToEdit)
{
Trasa trasaOriginal = _trasaRepository.FindById(trasaId);
trasaOriginal.Nazwa = trasaToEdit.Trasa.Nazwa;
foreach(KlientDoTrasa kdt in trasaOriginal.KlientDoTrasa.ToList())
{
_klientDoTrasaRepository.Remove(kdt);
}
for(int i = 0; i < trasaToEdit.Klienci.Count; i++)
{
var kdt = new KlientDoTrasa {Trasa = trasaOriginal, KlientId = trasaToEdit.Klienci[i].Id, Seq = i};
_klientDoTrasaRepository.Add(kdt);
}
_klientDoTrasaRepository.SaveChanges();
_trasaRepository.SaveChanges();
}
Entity Framework does not do a deep comparison of your entities to determine whether they are equivalent. Your code above will delete then insert, assuming that the two entities are different.
If you want to avoid updating an Entity that hasn't changed, you'll need to check for that in your own logic. I believe you could use a partial class declaration to implement IEqualityComparer for your entities, then compare before submit.
Related
I have an ASP.NET MVC app using Entity Framework from our SQL Server backend.
Goal is to create ~18 WPackage entries via a foreach loop:
foreach (var dbitem in dbCList)
The code works for a single WPackage entry, but we have a request from the customer to create 300+ WPackages, so trying to use the Entity Framework code for a single "Add" and loop to create 300+ adds.
The T-SQL would be very challenging as there are many keys created on the fly/at row creation, so for activities >> resources, we'd have to insert the activity, grab or remember the activity key, then add resources with that newly created activity key.
Each WPackage (this is the main parent table) could have one or more of the following child table entries:
1+ activities
each activity would have 1+ resource
1+ budgets
1+ Signatures
1+ CostCodes
Our schema or model diagram would be:
WPackage
--Activities
-----Resources (child of Activities)
--CostCodes
--Budgets
--Signatures
The following code fails on:
dbContextTransaction.Commit();
with an error:
The transaction operation cannot be performed because there are pending requests working on this transaction.
[HttpPost]
public ActionResult Copy([Bind(Include = "ID,WBSID,...***fields excluded for brevity")] Package model)
{
if (ModelState.IsValid)
{
try
{
using (var dbContextTransaction = db.Database.BeginTransaction())
{
var dbCList = db.Packages.Join(db.WBS,
*expression omitted for brevity*)
// this dbClist will build about 18 items in the collection for below loop
foreach (var dbitem in dbCList)
{
int testWPID = dbitem;
WPackage prvWP = db.WPackages.Find(dbitem);
int previousWPID = dbitem;
WPackage previousWP = db.WPackages.Find(dbitem);
model.ID = dbitem;
db.WPackages.Add(model);
db.SaveChanges();
var budgets = db.Budgets.Where(i => i.WPID == previousWPID);
foreach (Budget budget in budgets)
{
budget.WPID = model.ID;
db.Budgets.Add(budget);
}
var costCodes = db.CostCodes.Where(i => i.WPID == previousWPID);
foreach (CostCode costCode in costCodes)
{
costCode.WPID = model.ID;
db.CostCodes.Add(costCode);
}
var activities = db.Activities.Where(i => i.WPID == previousWPID);
// *code excluded for brevity*
var previousActivityID = activity.ID;
db.Activities.Add(activity);
db.SaveChanges();
var resources = db.Resources.Where(i => i.ActivityID == previousActivityID);
foreach (Resource resource in resources)
{
resource.WPID = model.ID;
resource.ActivityID = activity.ID;
resource.ActivityNumber = activity.ActivityNumber;
db.Resources.Add(resource);
db.SaveChanges();
}
}
var signatures = db.RolesAndSigs
.Where(i => i.KeyId == previousWPID && i.Type == "WPL")
.OrderBy(i => i.Role)
.OrderBy(i => i.Person);
foreach (RolesAndSig signature in signatures)
{
db.RolesAndSigss.Add(signature);
}
db.SaveChanges();
dbContextTransaction.Commit();
}
}
}
}
I've also tried to have the Commit() run outside the foreach dbitem loop like:
db.SaveChanges();
//dbContextTransaction.Commit();
}
dbContextTransaction.Commit();
...but this returns error of:
[EXCEPTION] The property 'ID' is part of the object's key information and cannot be modified.
The code you posted has some issues that don't make sense, and probably aren't doing what you think they are doing. The crux of the issue you are facing is that Entity Framework tracks all references to entities it loads and associates:
Firstly this code:
int testWPID = dbitem;
WPackage prvWP = db.WPackages.Find(dbitem);
int previousWPID = dbitem;
WPackage previousWP = db.WPackages.Find(dbitem);
prvWP and previousWP will be pointing to the exact same reference, not two copies of the same entity. Be careful when updating either or any other reference retrieved or associated with that same ID. They all point to the same instance. If you do want a stand-alone snaphot reference you can use AsNoTracking().
Next, when you do something like this in a loop:
model.ID = dbitem;
db.WPackages.Add(model);
In the first iteration, "model" is not an entity. It is a deserialized block of data with the Type of the Package entity. As soon as you call .Add(model) that reference will now be pointing to a newly tracked entity reference. In the next loop you are telling EF to change that tracked entity reference's ID to a new value, and that is illegal.
What it looks like you want to do is create a copy of this model for each of the 18 expected iterations. For that what you want to do would be something more like:
foreach (var dbitem in dbCList)
{
var newModel = new WPackage
{
ID = dbItem,
WBSID = model.WBSID,
/// copy across all relevant fields from the passed in model.
};
db.WPackages.Add(newModel);
// ...
}
It would be quite worthwhile to leverage navigation properties for the related entities rather than using explicit joins and trying to scope everything in an explicit transaction with multiple SaveChanges() calls. EF can manage all of the FKs automatically rather than essentially using it as a wrapper for individual ADO CRUD operations.
You will need to be explicit between when you want to "clone" an object reference vs. "copy" a reference. For example, if I have a Customer that has an Address, and Addresses have a Country reference, when I clone a Customer, I will want to clone a new Address record for that Customer, however ensure that the Country reference is copied across. If I have a record for Jack at an 123 Apple Street, London in England, and go to clone Jack to make a record for Jill at the same address, they might be at the same location now, but not always, so I want them to point at different Address records in case Jill moves out. Still, there should only be one record for "England". (Jill may move to a different country, but her address record would just point at a different Country Id)
Wrong:
var jill = context.Customers.Single(c => c.Name == "Jack");
jill.Name = "Jill";
context.Customers.Add(jill);
This would attempt to rename Jack into Jill, then "Add" the already tracked instance, resulting in an exception.
Will work, but still Wrong:
var jack = context.Customers.AsNoTracking().Single(c => c.Name == "Jack");
var jill = jack;
jill.Name = "Jill";
context.Customers.Add(jill);
This would technically work by loading Jack as an untracked entity, and would save Jill as a new record with a new Id. However this is potentially very confusing. Depending on how the AddressId/Address is referenced we could end up with Jack and Jill referencing the same single Address record. Bad if you want Jack and Jill to have different addresses.
Right:
var jack = context.Customers
.Include(c => c.Address)
.ThenInclude(a => a.Country)
.Single(c => c.Name == "Jack");
var jill = new Customer
{
Name = "Jill",
// copy other fields...
Address = new Address
{
StreetNumber = jack.Address.StreetNumber,
StreetName = jack.Address.StreetName,
Country = jack.Address.Country
}
};
context.Customers.Add(jill);
The first detail is to ensure when we load Jack that we eager load all of the related details we will want to clone or copy references to. We then create a new instance for Jill, copying the values from Jack, including setting up a new Address record. The Country reference is copied across as there should only be ever a single record for "England".
Edit: For something like a roll-over scenario if you have a package by year, let's use the example of a Package class below:
public class Package
{
[Key]
public int PackageId { get; set; }
[ForeignKey("PackageType")]
public int PackageTypeId { get; set; }
public int Year { get; set; }
// .. More package related details and relationships...
public virtual PackageType PackageType { get; set; }
}
A goal might be to make a new Package and related data for Year 2022 from the data from 2021, and apply any changes from a view model passed in.
Find is a poor choice for this because Find wants to locate data by PK. If you're method simply passes an entity to be copied from (I.e. the data from 2021) then this can work, however if you have modified that data from 2021 to represent values you want for 2022 that could be dangerous or misleading within the code. (We don't want to update 2021's data, we want to create a new record set for 2022) To make a new Package for 2022 we just need the updated data to make up that new item, and a way to identify a source for what to use as a template. That identification could be the PK of the row to copy from (ProductId), or derived from the data passed in. (ProductTypeId, and Year-1) In both cases if we want to consider related data with the "copy from" product then it would be prudent to eager load that related data in one query rather than going back to the database repeatedly. Find cannot accommodate that.
For instance if I want to pass data to make a new product I pass a ProductTypeId, and a Year along with any values to use for the new structure. I can attempt to get a copy of the existing year to use as a template via:
var existingProduct = context.Products
.Include(x => x.Activities) // Eager load related data.
.Include(x => x.CostCodes)
// ...
.Single(x => x.ProductTypeId == productTypeId && x.Year = year - 1);
or if I passed a ProductId: (such as if I could choose to copy the data from a selected year like 2020 instead)
var existingProduct = context.Products
.Include(x => x.Activities)
.Include(x => x.CostCodes)
// ...
.Single(x => x.ProductId == copyFromProductId);
Both of these examples expect to find one, and only one existing product. If the request comes in with values that it cannot find a row for, there would be an exception which should be handled. This would fetch all of the existing product information that we can copy from, alongside any data that was passed into the method to create a new Product.
I saw this code work with LINQ to SQL but when I use Entity Framework, it throws this error:
LINQ to Entities does not recognize the method 'System.Linq.IQueryable'1[MyProject.Models.CommunityFeatures] GetCommunityFeatures()' method, and this method cannot be translated into a store expression.`
The repository code is this:
public IQueryable<Models.Estate> GetEstates()
{
return from e in entity.Estates
let AllCommFeat = GetCommunityFeatures()
let AllHomeFeat = GetHomeFeatures()
select new Models.Estate
{
EstateId = e.EstateId,
AllHomeFeatures = new LazyList<HomeFeatures>(AllHomeFeat),
AllCommunityFeatures = new LazyList<CommunityFeatures>(AllCommFeat)
};
}
public IQueryable<Models.CommunityFeatures> GetCommunityFeatures()
{
return from f in entity.CommunityFeatures
select new CommunityFeatures
{
Name = f.CommunityFeature1,
CommunityFeatureId = f.CommunityFeatureId
};
}
public IQueryable<Models.HomeFeatures> GetHomeFeatures()
{
return from f in entity.HomeFeatures
select new HomeFeatures()
{
Name = f.HomeFeature1,
HomeFeatureId = f.HomeFeatureId
};
}
LazyList is a List that extends the power of IQueryable.
Could someone explain why this error occurs?
Reason:
By design, LINQ to Entities requires the whole LINQ query expression to be translated to a server query. Only a few uncorrelated subexpressions (expressions in the query that do not depend on the results from the server) are evaluated on the client before the query is translated. Arbitrary method invocations that do not have a known translation, like GetHomeFeatures() in this case, are not supported.
To be more specific, LINQ to Entities only support Parameterless constructors and Initializers.
Solution:
Therefore, to get over this exception you need to merge your sub query into the main one for GetCommunityFeatures() and GetHomeFeatures() instead of directly invoking methods from within the LINQ query. Also, there is an issue on the lines that you were trying to instantiate a new instance of LazyList using its parameterized constructors, just as you might have been doing in LINQ to SQL. For that the solution would be to switch to client evaluation of LINQ queries (LINQ to Objects). This will require you to invoke the AsEnumerable method for your LINQ to Entities queries prior to calling the LazyList constructor.
Something like this should work:
public IQueryable<Models.Estate> GetEstates()
{
return from e in entity.Estates.AsEnumerable()
let AllCommFeat = from f in entity.CommunityFeatures
select new CommunityFeatures {
Name = f.CommunityFeature1,
CommunityFeatureId = f.CommunityFeatureId
},
let AllHomeFeat = from f in entity.HomeFeatures
select new HomeFeatures() {
Name = f.HomeFeature1,
HomeFeatureId = f.HomeFeatureId
},
select new Models.Estate {
EstateId = e.EstateId,
AllHomeFeatures = new LazyList<HomeFeatures>(AllHomeFeat),
AllCommunityFeatures = new LazyList<CommunityFeatures>(AllCommFeat)
};
}
More Info: Please take a look at LINQ to Entities, what is not supported? for more info.
Also check out LINQ to Entities, Workarounds on what is not supported for a detailed discussion on the possible solutions.
(Both links are the cached versions because the original website is down)
Some background
I'm wanting to bind a list of objects (my model-view) to a grid. The model-view contains fields for both an specific entity and fields from a joined entity.
I was getting an error when I would try to bind due to the dbContext being out of scope. I realized I needed to use the .Include() method in order to eager load my navigation property. However, I suspect that since I'm using Linq to Entities, that I'm now generating another error:
"Unable to cast the type 'System.Linq.IQueryable1' to type 'System.Data.Objects.ObjectQuery1'. LINQ to Entities only supports casting EDM primitive or enumeration types."
My code is shown below, any ideas of what I need to do here?
Thanks in advance!
public static List<PlanViewModel> GetPlans()
{
using (var context = new RepEntities())
{
var query = (from p in context.Plans
join r in context.RealEstateDetails on p.ReId equals r.ReId
select new PlanViewModel
{
PlanName = p.PlanName,
TargetCompletionDate = p.TargetCompletionDate,
ActualCompletionDate = p.ActualCompletionDate,
Provision = p.Provision,
StatusTypeId = p.StatusTypeId,
StatusCommon = p.StatusCommon,
Building = r.BuildingName,
City = r.City,
Country = r.Country
}).Include("StatusCommon");
return query.ToList();
}
}
You are almost there, just put Include("StatusCommon") right after context.Plans. Because you need to include StatusCommon before the iteration, this way you can set StatusCommon value for every iteration.
public static List<PlanViewModel> GetPlans()
{
using (var context = new RepEntities())
{
var query = (from p in context.Plans.Include("StatusCommon")
join r in context.RealEstateDetails on p.ReId equals r.ReId
select new PlanViewModel
{
PlanName = p.PlanName,
TargetCompletionDate = p.TargetCompletionDate,
ActualCompletionDate = p.ActualCompletionDate,
Provision = p.Provision,
StatusTypeId = p.StatusTypeId,
StatusCommon = p.StatusCommon,
Building = r.BuildingName,
City = r.City,
Country = r.Country
}).toList();
return query;
}
}
This query produces an error No value given for one or more required parameters:
using (var conn = new OleDbConnection("Provider=..."))
{
conn.Open();
var result = conn.Query(
"select code, name from mytable where id = ? order by name",
new { id = 1 });
}
If I change the query string to: ... where id = #id ..., I will get an error: Must declare the scalar variable "#id".
How do I construct the query string and how do I pass the parameter?
The following should work:
var result = conn.Query(
"select code, name from mytable where id = ?id? order by name",
new { id = 1 });
Important: see newer answer
In the current build, the answer to that would be "no", for two reasons:
the code attempts to filter unused parameters - and is currently removing all of them because it can't find anything like #id, :id or ?id in the sql
the code for adding values from types uses an arbitrary (well, ok: alphabetical) order for the parameters (because reflection does not make any guarantees about the order of members), making positional anonymous arguments unstable
The good news is that both of these are fixable
we can make the filtering behaviour conditional
we can detect the category of types that has a constructor that matches all the property names, and use the constructor argument positions to determine the synthetic order of the properties - anonymous types fall into this category
Making those changes to my local clone, the following now passes:
// see https://stackoverflow.com/q/18847510/23354
public void TestOleDbParameters()
{
using (var conn = new System.Data.OleDb.OleDbConnection(
Program.OleDbConnectionString))
{
var row = conn.Query("select Id = ?, Age = ?", new DynamicParameters(
new { foo = 12, bar = 23 } // these names DO NOT MATTER!!!
) { RemoveUnused = false } ).Single();
int age = row.Age;
int id = row.Id;
age.IsEqualTo(23);
id.IsEqualTo(12);
}
}
Note that I'm currently using DynamicParameters here to avoid adding even more overloads to Query / Query<T> - because this would need to be added to a considerable number of methods. Adding it to DynamicParameters solves it in one place.
I'm open to feedback before I push this - does that look usable to you?
Edit: with the addition of a funky smellsLikeOleDb (no, not a joke), we can now do this even more directly:
// see https://stackoverflow.com/q/18847510/23354
public void TestOleDbParameters()
{
using (var conn = new System.Data.OleDb.OleDbConnection(
Program.OleDbConnectionString))
{
var row = conn.Query("select Id = ?, Age = ?",
new { foo = 12, bar = 23 } // these names DO NOT MATTER!!!
).Single();
int age = row.Age;
int id = row.Id;
age.IsEqualTo(23);
id.IsEqualTo(12);
}
}
I've trialing use of Dapper within my software product which is using odbc connections (at the moment). However one day I intend to move away from odbc and use a different pattern for supporting different RDBMS products. However, my problem with solution implementation is 2 fold:
I want to write SQL code with parameters that conform to different back-ends, and so I want to be writing named parameters in my SQL now so that I don't have go back and re-do it later.
I don't want to rely on getting the order of my properties in line with my ?. This is bad. So my suggestion is to please add support for Named Parameters for odbc.
In the mean time I have hacked together a solution that allows me to do this with Dapper. Essentially I have a routine that replaces the named parameters with ? and also rebuilds the parameter object making sure the parameters are in the correct order.
However looking at the Dapper code, I can see that I've repeated some of what dapper is doing anyway, effectively it each parameter value is now visited once more than what would be necessary. This becomes more of an issue for bulk updates/inserts.
But at least it seems to work for me o.k...
I borrowed a bit of code from here to form part of my solution...
The ? for parameters was part of the solution for me, but it only works with integers, like ID. It still fails for strings because the parameter length isn't specifed.
OdbcException: ERROR [HY104] [Microsoft][ODBC Microsoft Access Driver]Invalid precision value
System.Data.Odbc. OdbcParameter.Bind(OdbcStatementHandle hstmt,
OdbcCommand command, short ordinal, CNativeBuffer parameterBuffer, bool allowReentrance)
System.Data.Odbc.OdbcParameterCollection.Bind(OdbcCommand command, CMDWrapper cmdWrapper, CNativeBuffer parameterBuffer)
System.Data.Odbc.OdbcCommand.ExecuteReaderObject(CommandBehavior behavior, string method, bool needReader, object[] methodArguments, SQL_API odbcApiMethod)
System.Data.Odbc.OdbcCommand.ExecuteReaderObject(CommandBehavior behavior, string method, bool needReader)
System.Data.Common.DbCommand.ExecuteDbDataReaderAsync(CommandBehavior behavior, CancellationToken cancellationToken)
Dapper.SqlMapper.QueryAsync(IDbConnection cnn, Type effectiveType, CommandDefinition command) in SqlMapper.Async.cs
WebAPI.DataAccess.CustomerRepository.GetByState(string state) in Repository.cs
var result = await conn.QueryAsync(sQuery, new { State = state });
WebAPI.Controllers.CustomerController.GetByState(string state) in CustomerController .cs
return await _customerRepo.GetByState(state);
For Dapper to pass string parameters to ODBC I had to specify the length.
var result = await conn.QueryAsync<Customer>(sQuery, new { State = new DbString { Value = state, IsFixedLength = true, Length = 4} });
I'm trying to do something similar to this post where I don't pull back all columns from a particular entity, however my framework makes use of inheritence and I lose scope of the entity type after it's been cast to an anonymous type.
The structure of my Entity Framework has a base entity called Action. From here I've created two inherited entities called Event and Activity. I want to pull back the last X Actions and pass them to my strongly typed view which accepts an Action and from there determines if its an Activity or Event and renders the correct partial view.
if(Model.GetType() == typeof(Event))
{
//render Event view
}
else if(Model.GetType() == typeof(Activity))
{
//render Activity view
}
I can pull the last 10 as an anonymous type and then cast:
var result = from a in new DataContext().Actions
where a.UserId == someGuidValue
select new { a.CreatedOn, a.Summary };
List<Action> list = result.AsEnumerable()
.Select(o => new Action {
CreatedOn = o.CreatedOn,
Summary = o.Summary
}).ToList();
However, once I pass the new List of Actions to my strongly typed view it loses scope of whether it's an Activity or an Event since it's been cast as an Action. My question is, without exposing the discriminator column, is there any way to cast each item to the proper type or am I going about this the wrong way?
A bit kludgy, but will work:
var result = from a in new DataContext().Actions
where a.UserId == someGuidValue
let IsEvent = a as Event != null
select new { a.CreatedOn, IsEvent, a.Summary };
List<Action> list = result.AsEnumerable()
.Select(o => o.IsEvent ?
(Action) new Event {
CreatedOn = o.CreatedOn,
Summary = o.Summary
}
: (Action) new Activity {
CreatedOn = o.CreatedOn,
Summary = o.Summary
}
}).ToList();
Example with type-specific columns, presuming that e.EventSpecific is of a nullable type.
var result = from a in new DataContext().Actions
where a.UserId == someGuidValue
let ev = a as Event
let IsEvent = ev != null
select new { a.CreatedOn, IsEvent, a.Summary, ev.EventSpecific };
List<Action> list = result.AsEnumerable()
.Select(o => o.IsEvent ?
(Action) new Event {
CreatedOn = o.CreatedOn,
Summary = o.Summary,
EventSpecific = o.EventSpecific
}
: (Action) new Activity {
CreatedOn = o.CreatedOn,
Summary = o.Summary,
EventSpecific = o.EventSpecific // will be null, but using o.EventSpecific saves casting
}
}).ToList();
If o.EventSpecific is of a non-nullable type, then you must convert it to a nullable type in the L2E query.
You are probably on the wrong way. At first I would assume that Action should be an abstract class and you should not be able to create instances of it at all. If you then only fetch a subset of the properties and the subset does no longer allow to discriminate between events and activities, it is probably the wrong way to try making events and activities out of them.
So it actually seems not to be a technical problem - it should be quite easy to include some discrimination information in the anonymous type - but a design problem. I suggest to rethink if it is required to discriminate the query result and if so if it is really a good idea to discriminate the result in absence of an discriminator.