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.
Related
I have an ApiController that uses Entity Framework/LINQ to SQL for data access. For a PUT operation I am passing in a "Theme" object which has a string property "Path" which I need to inspect to see if has changed from what is currently in the database. If it has changed, I need to perform an additional action of changing the name of a directory.
I wrote some code to detect this, putting it after checking the ModelState.IsValid property and setting the entry's state to EntityState.Modified. When I was testing it I did not see the behavior I was expecting. I used LINQ to find the current record using the passed-in ID and the value of the property showed the same value as the same property of the object I passed in. As a result, the expression in my if statement evaluates to false and the additional action doesn't occur. However, when I use SQL Management Studio to query the database, the value of the field I'm using in the comparison is what I was expecting.
I've tried getting the current value by calling a separate method that returns a string but I get the same result. If I do this lookup at the beginning of my PUT method, I get an InvalidOperationException:
Attaching an entity of type 'DataAccess.Models.Theme' failed because
another entity of the same type already has the same primary key
value. This can happen when using the 'Attach' method or setting the
state of an entity to 'Unchanged' or 'Modified' if any entities in the
graph have conflicting key values. This may be because some entities
are new and have not yet received database-generated key values. In
this case use the 'Add' method or the 'Added' entity state to track
the graph and then set the state of non-new entities to 'Unchanged' or
'Modified' as appropriate.
Here's my code:
public async Task<IHttpActionResult> PutTheme(int id, Theme theme)
{
if (theme == null)
return BadRequest();
if (theme.ID != id)
return BadRequest();
if (!ModelState.IsValid)
return BadRequest(ModelState);
_db.Entry(theme).State = EntityState.Modified;
// We need to detect whether the theme path changed, and if so, we need to rename the theme folder
var previousTheme = await _db.Themes.FindAsync(id);
// We can't do this because the Path property will match the Path value of the passed-in theme
if ((previousTheme != null) && (theme.Path != previousTheme.Path))
RenameThemeDirectory(id, previousTheme.Path, theme.Path);
// Remaining code to save data here
}
How can I do this without passing into my method the original Path property value to be used in the comparison?
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.
I've written a class validator as a service and passed the doctrine entity manager to this validator. At this point everything works fine.
But now I need the unchanged object of $entry which is been updated in the form - or at least the previous values. I've tried some approaches, but did not succeed:
public function isValid($entry, Constraint $constraint)
{
$oldEntry = $this->em->getRepository('SomeBundle:Entry')->findOneBy(array('id' => $entry->getId()));
Doctrine fetches the same (changed) object as expected. But trying to refresh the object will reset both versions of the object:
$newEntry = clone $entry;
$this->em->detach($newEntry);
$this->em->refresh($entry);
$hoursOfOldEntry = $entry->calculateHours();
$this->em->merge($newEntry);
Another option could be to save the values of the object as array, refresh the object and reassign the saved values again after working on the original values. But this does not seem to be the best way, especially if the are many relations. I don't wont to touch the object within a validator, I just need the previous values!
Another approach could be using Doctrine\ORM\UnitOfWork#recomputeSingleEntityChangeSet(Doctrine\ORM\ClassMetadata $meta, $entity). But I don't think it's a good idea to use internal doctrine methods in a validator!
So how do I get the original object or the change set in a class validator?
This won't get you the original entity, but should get you a key/value array of the original fields:
$uow = $em->getUnitOfWork();
$originalData = $uow->getOriginalEntityData($entry);
http://www.doctrine-project.org/api/orm/2.0/source-class-Doctrine.ORM.UnitOfWork.html#2210
I'm using Play Framework 2 and Ebean. When a user submits a form to edit an existing object in the database, it doesn't save null values. I guess this is to prevent overwriting fields that aren't in the form with null. But how can I let them set fields in the form to null if they need to?
For example, the user edits an Event object. Event.date is 1/1/13. The user sets the Event.date field in the form to empty and submits the form. Inspecting Event.date in the debugger shows its value is null. I save the Event. If I look at the Event in the database, its value is still 1/1/13.
Edit: It seems there is a method for this. The only problem is it doesn't work on nested entities. Any solutions for this?
update(Object bean,Set<String> properties)
Create an ebean.properties file right next to the application.conf file and add this line to it:
ebean.defaultUpdateNullProperties=true
Null properties in Ebean are considered as unloaded, so to prevent accidental nulling properties that shouldn't be nulled, they are just excluded.
Because of this reverting Date (and other fields) to null in Ebean is... hard :). Last time when I had to do the same thing (revert Date) I used second query to do just... nulling the Date (after event.update(Object o)):
public static Result updateEvent(){
Form<Event> eventForm = form(Event.class).bindFromRequest();
// do some validation if required...
Event event = eventForm.get();
event.update(event.id);
if (eventForm.get().date == null){
Ebean
.createUpdate(Event.class, "UPDATE event SET date=null where id=:id")
.setParameter("id", page.id).execute();
}
}
On the other hand, if you are using comparison, for filtering events (always selecting newer than X), you can just set the date to very 'old' value, which also should do the trick. In this case you'll update the object only once.
private static final Date VERY_OLD_DATE = new GregorianCalendar(1, 0, 1).getTime();
public static Result updateEvent(){
Form<Event> eventForm = form(Event.class).bindFromRequest();
Event event = eventForm.get();
if (eventForm.get().date == null){
event.date = VERY_OLD_DATE;
}
event.update(event.id);
}
In this case in your HTML form you will need to clear the value of the form's field (or just send every time date like 0001-01-01), however it can be done easily even with JavaScript.
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();