Including child Objects in Entityframework - entity-framework

I want to include child objects on an IQueryable list..
I want to include a child object on selected columns of some table type IQueryable list..
I tried like this:
IQueryable<Persons> persons = Context.Persons.Select(x=> new persons{Pkid=x.pkid, FirstName=x.FirstName}).AsQueryable();
persons= persons.Include("Address");
this include of child objects is not working..anyone please help...where I am doing wrong..
thanks alot...

Include doesn't work with projection. Moreover it is not needed. Just do this:
var query = context.Persons
.Select(x => new PersonDto
{
Id = x.pkid,
FirstName = x.FirstName,
Address = x.Address
});
Few points here:
No Include
Address accessed directly in projection, EF will handle this
I'm using PersonDto as target of projection. PersonDto has just Id, FirstName and Address.
You can project to custom type or anonymous type but you cannot project to entity type (the mapped type) - it doesn't work and it throws exception.
If you want to use mapped type you can't return only selected scalar columns - all columns will always be loaded. Only navigation properties can be loaded selectively. To overcome this people sometimes use Table splitting but that is something which works if you can divide your big entity into disjunct entities. In your scenario use just projection.

You cannot use Include() on a projection, try this:
Iquerable<Persons> persons = Context.Persons
.Include("Address")
.Select(x=> new persons{Pkid=x.pkid, FirstName=x.FirstName})
.AsQuerable();
Also you have a naming conflict, you project to a type persons and want to hold the results in an IQueryable named persons - one of them is wrong. Is there a reason you need the projection at all? You could just do
Iquerable<Persons> persons = Context.Persons.Include("Address");

First: Check if lazy loading is enabled or not. I experienced different results when it was enabled. I prefer lazy loading being disabled.
Second: Check this syntax:
result = (From person In context.Persons.Include("Address")).ToList();
P.S.: Useful EF Tips & Tricks : http://blogs.msdn.com/b/alexj/archive/2009/03/26/index-of-tips.aspx
UPDATE:
Include is not working, because your are using it on newly created objects, not the objects available in the context. you should use Include before creating new objects.
Check This:
result = (From person In context.Persons.Include("Address") Select New With {.FirstName = item.FirstName, .AddressValue = item.Address.Value}).ToList();

Related

Add SQL restriction to predicates in JPA query

I have to filter entities according to some parameters sent by client. For this purpose, i create a list of predicates like this:
List<Predicate> predicates = new ArrayList<Predicate>();
if (filters != null && StringUtils.hasText(filters.getName())) {
predicates.add(cb.like(cb.upper(root.get("name")),
"%" + filters.getName().trim().toUpperCase() + "%"));
}
//OTHER FILTERS
Now the problem is to add a criteria that is sql syntax. In particular i have to find entities that are located into a particular polygon. So i should add a restriction like this:
and within(point, :bounds) = true //bounds is the geometry drawn by client
I have read that i could use #Formula to define an sql filter but this annotation works everytime even if filter in input(about localization) is not setted.
Can anyone help me?
You should be able to call database functions using CriteriaBuilder.function(...). Try cb.equal(cb.function("within", Boolean.class, root.get("point"), bounds), cb.literal(true)).
This may or may not work out of the box depending on the type of the bounds parameter, because Hibernate needs to recognize it to know its SQL representation, though. You might need to create a custom LiteralType

Lookup Edit binding

I have a model written using Entity Framework Code First called Project.
In my UI, there is a page called ProjectEdit as shown in the image below. As seen in the image below, Customer and BOMs are Lookup Edit.
I'm trying to load Customer and BOMs to Lookup Edit but it's not working. Below is my code.
//New
if (entity == null)
{
Entity = new Project();
}
//Edit
else
{
ProjectCodeTextEdit.DataBindings.Add("EditValue", entity, "ProjectCode");
DescriptionTextEdit.DataBindings.Add("EditValue", entity, "Description");
CustomerLookUpEdit.DataBindings.Add("EditValue", entity, "CustomerId");
BOMsLookUpEdit.DataBindings.Add("EditValue", entity, "BOMs");
}
Below is my LookUpEdit Properties.
Generally LookUpEdit object's data binding is not implemented the same way as a TextEdit object's. While in TextEdits's case you just need to assign the variable value to EditValue property (I suppose your TextEdits binding work fine, isn't it?), with LookUp Edit you should assign variables to ValueMember and a DisplayMember properties of the object. That is why we usually display data rows with LookUpEdit objects, where ValueMember is the identification field of the row and DisplayMember is the field of the row whose value you wish to be displayed.
In your case you should be more clear about what you wish to display in your lookupedits. Each Project instance has one Customer property and many BOMs, right? So CustomerLookUpEdit will show one record and BOMsLookUpEdit a list of values according to the Project object that was chosen for edit, correct? I suppose that both your Customer and BOM classes have some kind of ID property and description property of their own. In this case you should bind these values to the LookUpEdits. eg. in your initialization function code add these lines
CustomerLookUpEdit.Properties.DataSource = entity.Customer;
CustomerLookUpEdit.Properties.ValueMember = "someCustomerIDpropertyName" ;
CustomerLookUpEdit.Properties.DisplayMember = "someCustomerDescriptionpropertyName";
BOMsLookUpEdit.Properties.DataSource = entity.BOMs;
BOMsLookUpEdit.Properties.ValueMember = "someBOMIDpropertyName" ;
BOMsLookUpEdit.Properties.DisplayMember = "someBOMDescriptionpropertyName" ;
You can read more in this topic https://documentation.devexpress.com/#WindowsForms/clsDevExpressXtraEditorsLookUpEdittopic
When we are adding entities to a List, we have to take care of our DataSource if is a DBContext or a DBSet, each one has implications in the compiler, that was your case, in this case you had to especify your DataSource like a DBSet and get the Entities
Add<TEntity>(TEntity entity)
The type parameter omitted is posible because the compiler will infer it.

Getting the column name (sspace) from an ospace property name

I can see from the following example how to get the table name of an OSpace type:
https://lowrymedia.com/2014/06/10/ef6-1-mapping-between-types-tables-including-derived-types/
But how do I go about getting the SSpace column name from an OSpace property name (i.e. CLR type property)?
By browsing the MetadataProperties from the corresponding CSpace property, I can see there is a "Configuration" entry containing the column name if changed using the Fluid API or ColumnAttribute, but the value of the entry is an internal class on EF's part. Is it at all possible?
I have browsed a few answers regarding this topic, but none of them take into account the Fluid API configuration.
P.S. the specific property I'm looking for is scalar, if that can simplify things...
Column Name
To get the column name, you have to first get the EdmProperty associated with that column in the “structural space” (SSpace). I provide code to do that below. Once you have the EdmProperty, the name of the column is simply EdmProperty.Name:
string GetColumnName(DbContext context, PropertyInfo property) {
return GetStructuralSpaceEdmProperty(context, property).Name;
}
Structural Space Property
This is based on an article. That article gives you enough information to map all the way to the structural EntityType. I added a bit at the end to do the actual property mapping to get the EdmProperty representing the column. As the article states, these APIs require ≥EntityFramework-6.1.
EdmProperty GetStructuralSpaceEdmProperty(DbContext context, PropertyInfo property) {
IObjectContextAdapter adapter = context;
var metadata = adapter.ObjectContext.MetadataWorkspace;
// First, you map the Object Space to the Conceptual Space.
var objectItemCollection = (ObjectItemCollection)metadata.GetItemCollection(DataSpace.OSpace);
var objectEntityType = metadata.GetItems<EntityType>(DataSpace.OSpace)
.Single(oet => objectItemCollection.GetClrType(oet) == property.DeclaringType);
// Note: we are assuming that CSpace and OSpace name their properties the
// same instead of trying to use EF’s own OSSpace mappings here.
var conceptualEntityType = metadata.GetItems<EntityType>(DataSpace.CSpace)
.Single(cet => objectEntityType.Name == cet.Name);
var conceptualEdmProperty = conceptualEntityType.Properties
.Single(ep => ep.Name == property.Name);
// Then you map the conceptual space onto the structural space.
var entitySet = metadata.GetItems<EntityContainer>(DataSpace.CSpace)
.Single().EntitySets
.Single(es => es.ElementType.Name == conceptualEntityType.Name);
var entityMapping = metadata.GetItems<EntityContainerMapping>(DataSpace.CSSpace)
.Single().EntitySetMappings
.Single(esm => esm.EntitySet == entitySet);
// The entity may be split to different tables or fragments.
var fragments = entityMapping.EntityTypeMappings
.SelectMany(etm => etm.Fragments);
var propertyMappings = fragments.SelectMany(f => f.PropertyMappings);
// Normal properties will be “ScalarPropertyMapping”.
// Depending on what information you are seeking or your
// model, you may be interested in other PropertyMapping.
var structuralSpaceProperty = propertyMappings
.OfType<ScalarPropertyMapping>()
.Single(pm => pm.Property == conceptualEdmProperty).Column;
return structuralSpaceProperty;
}
Note that once you have EdmProperty in structural space, there are a bunch of other useful properties you can read from it. For example, for SQL Server, EdmProperty.IsUnicode will be true for NVARCHAR/NCHAR and false for VARCHAR/CHAR types whereas this property is not set to a useful value in the conceptual space.
Random Information
Spaces in EF
Alex D. James’s blog post “Tip 10 — How to understand Entity Framework jargon” explains some of the terms of the API which do not make sense on their own. DataSpace.OSpace stands for “Object Space”, meaning the .net POD classes. DataSpace.SSpace stands for “Structural Space”, probably named after “structured” in the term “SQL” and thus meaning it most directly describes the backend database. DataSpace.CSpace stands for “Conceptual Space” which seems intended to be a neutral space which both the “Object Space” and “Structural Space” can map into. DataSpace.OCSpace stands for the mapping from the object space onto the conceptual space. We bypass this mapping because we assume that property names in the object space are the same as in our .net types. DataSpace.CSSpace stands for the mapping of conceptual space onto structural space. We use this mapping because the model may be configured to use a different column name via the fluent API or ColumnAttribute.
API Confusion
The metadata API of EF seems to assume that the consumer of the API has an understanding of the internals of EF to an extent. It is not made in a very type safe way which helps consumers. For example, the fact that we had to use Enumerable.OfType<TResult> to get to ScalarPropertyMapping means that one has to know to expect the collection to have ScalarPropertyMapping instances in it. Likewise, the MetadataWorkspace.GetItems<T>() method requires us to know that the sorts of items one would find in the metadata include EntityType. Thus, a deep understanding of the internals of EF or complete examples are necessary to write code that consumes the mapping portion of these APIs.

Custom display in CRUDified object

I have a an entity referencing another entity by MappedLongForeignKey.
I am using the CRUDify trait and have a problem.
Entity 1:
id
title (String)
validTo (Date)
Entity 2:
id
...
fk_entity_1 (mapped via MappedLongForeignKey)
In the listings generated by CRUDify for entity 2 I would like to include a column formatted as
fk_entity_1.title ( fk_entity_1.validTo )
I tried to create a function returning such a string and adding that fn to fieldsForDisplay, but it seems fieldsForDisplay requires mapped fields.
Is this possible to accomplish?
* Edit *
What I am trying to accomplish is (using the built in functionality of CRUDify for listings) produce listings as:
{Entity 2 fields} "Entity 1"
... Title_X (2001-01-01)
... Title_Y (2011-02-02)
If worse comes to worst, I can roll my own listings, but I really like the CRUDify functionality.
I'm not quite sure what you're trying to accomplish, but maybe you could override the asHtml method of the fields instead?

Symfony: Model Translation + Nested Set

I'm using Symfony 1.2 with Doctrine. I have a Place model with translations in two languages. This Place model has also a nested set behaviour.
I'm having problems now creating a new place that belongs to another node. I've tried two options but both of them fail:
1 option
$this->mergeForm(new PlaceTranslationForm($this->object->Translation[$lang->getCurrentCulture()]));
If I merge the form, what happens is that the value of the place_id field id an array. I suppose is because it is waiting a real object with an id. If I try to set place_id='' there is another error.
2 option
$this->mergeI18n(array($lang->getCurrentCulture()));
public function mergeI18n($cultures, $decorator = null)
{
if (!$this->isI18n())
{
throw new sfException(sprintf('The model "%s" is not internationalized.', $this->getModelName()));
}
$class = $this->getI18nFormClass();
foreach ($cultures as $culture)
{
$i18nObject = $this->object->Translation[$culture];
$i18n = new $class($i18nObject);
unset($i18n['id']);
$i18n->widgetSchema['lang'] = new sfWidgetFormInputHidden();
$this->mergeForm($i18n); // pass $culture too
}
}
Now the error is:
Couldn't hydrate. Found non-unique key mapping named 'lang'.
Looking at the sql, the id is not defined; so it can't be a duplicate record (I have a unique key (id, lang))
Any idea of what can be happening?
thanks!
It looks like the issues you are having are related to embedding forms within each other, which can be tricky. You will likely need to do things in the updateObject/bind methods of the parent form to get it to pass its values correctly to its child forms.
This article is worth a read:
http://www.blogs.uni-osnabrueck.de/rotapken/2009/03/13/symfony-merge-embedded-form/comment-page-1/
It gives some good info on how embedding (and mergeing) forms work. The technique the article uses will probably work for you, but I've not used I18n in sf before, so it may well be that there is a more elegant solution built in?