If you go to this website, http://www.asp.net/mvc/tutorials/getting-started-with-aspnet-mvc3/cs/intro-to-aspnet-mvc-3, you can see a tutorial where users create a movie database. I completed this tutorial with no problems, and attempted to create a new MVC application with some small changes that make the project more similar to what I want to do eventually.
Rather that create a model named Movie, I created one named Issue. Like movie, it has a few fields, but they are all different names and types. I went through the process exactly as is done in the tutorial, but whenever I try to add an issue to the database via the web UI, I get a DBEntityValidationException. I have not set any validation rules at this point in the process, so I am unsure of what the problem is.
Can someone give me some advice on fixing this so that I can add Issues to my database (as is done with movies on the online tutorial)?
Let me know if more information is needed; I am very new to this and may be lacking in details.
Here is the model code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
namespace MvcApplication200.Models
{
public class Issue
{
public String id { get; set; }
public DateTime created { get; set; }
public DateTime closed { get; set; }
public String summary { get; set; }
public bool? importToTFS { get; set; }
}
public class IssueDBContext : DbContext
{
public DbSet<Issue> Issues { get; set; }
}
}
Update:I just redid the whole process, but rather than have different fields and different types, I made it so that my Issue model had the same number and same types of fields (with only different names). The error went away, so the problem must be with db format or something. I hope this makes the problem more clear.
I just ended up adding this class, which removes everything from the database when fields are changed. Then, I refresh the database, which is easy to do in my situation. One could add some items to the Seed method in order to ensure that some things remain in the updated database after it is cleared.
public class IssueInitializer : DropCreateDatabaseIfModelChanges<IssueDBContext>
{
protected override void Seed(IssueDBContext context)
{
//add things here
}
}
Related
OK, so I've been building my first large(ish) EF 4.1 POCO + MVC application. It's a replacement of a legacy system so I 'm using an existing database.
I've generated my POCO classes using DbContext T4 generation. I've got some really nice forms going on and some really nice validation happening with a lot of sexy generics in my MVC classes to cut down on boiler-plate code... All's good.
Suddenly I realized that the most sensible thing (to me) would be for some of business logic to be in the "set" of some of the properties of my POCO objects.
E.g. Suppose the following class was generated by the T4;
public partial class SalesOrderLine
{
public int ID { get; set; }
public int SalesOrderID { get; set; }
public int ProductID { get; set; }
public decimal UnitPrice { get; set; }
public int Quantity { get; set; }
public decimal ExtendedPrice { get; set; }
public virtual Product Product { get; set; }
public virtual SalesOrder SalesOrder { get; set; }
}
Ignore for a moment the obvious argument that the calculated field "ExtendedPrice" shouldn't even be stored in the database, and just come along with me for the ride...
...then, it seems to me, logically, if this object is really supposed to represent a Sales Order Line, that I should be able to construct my object such that the following unit test will work:
SalesOrderLine sol = new SalesOrderLine();
sol.UnitPrice = 100;
sol.Quantity = 5;
Assert.IsEqual(sol.ExtendedPrice, 500);
...obviously I can't do that as long as I want the base POCO to be generated by the T4. It seems to me I have several options:
Set the generated code file's properties "do not compile", copy and paste the generated code into another file and modify the "set" to do the business logic of setting the extended price when the UnitPrice or Quantity is set. The downside here is that the logic will be run whenever an object is loaded from the database (since the EF will set the public properties and not my private fields). Additionally, this object will then need to be maintained manually for the rest of the life of the project when database changes occur.
Create an UpdateTotals function that gets called in the Validate routine that I have for my object, which gets called by the SaveChanges() on the DbContext. Obviously, the above Unit Test above would not work in that case. The system, and my integration tests however would work and would only call the code when a change was done to the object.
Decide that I'm asking the wrong question, and that I should really add methods to the object called "SetPrice" and "SetQuantity", and then qualify the set accessors of the UnitPrice and Quantity to be "internal". The downside here is that MVC will try and update the model from the form and won't be able to set those properties.
Some solution that involves downloading two or three more frameworks that create even more levels of abstraction than I already have... A repository pattern, or "use NHibernate" or something like that... You can suggest this, but I'm growing weary of how much work it is to set things up to do it the "academically correct" way. For this project, I'd rather meet halfway on the long-term-maintainability vs. speed-of-development spectrum and not over-complicate my project with a ton of extra tools and dlls... ...but I'll try an keep an open mind :)
--- EDIT: another idea ---
[5.] Another thought, since the fields are always simply calculated there should really be no need to ever set them - either from the database or otherwise. Therefore, something like this might work:
public decimal ExtendedAmount
{
get { return UnitPrice * Quantity; }
internal set { }
}
...my thought is that the EF instantiation would attempt to call the "set", but the set would do nothing, then, when the object was saved or checked for changes it would call the 'get' and that would return the calculated value and that value would get stored in the DB. The only downside here is when you were trying to use the object model to validate the database when the database had in incorrect value stored in the ExtendedAmount field. It's a little hokie, I know, but I thought it would be an interesting trick... in fact the "set" could perhaps throw an exception if (value != UnitPrice * Quantity)
--- END EDIT ---
I'm curious to hear what other have done in these kinds of cases, as I'm sure it's common. Seems like a lot of the tutorials take you as far as "generating POCO classes from the database", and then leave the rest of the project development up to you.
Cheers,
Chris
A couple ideas:
Why not use Code First? That way, you can put business logic (e.g., calculated properties) right in your entity class.
Example
public partial class SalesOrderLine
{
public int ID { get; set; }
public int SalesOrderID { get; set; }
public int ProductID { get; set; }
private decimal _unitPrice;
public decimal UnitPrice
{
get { return _unitPrice; }
set
{
if (value == _unitPrice) return;
_unitPrice = value;
CalculateExtendedPrice();
}
}
private decimal _quantity;
public decimal Quantity
{
get { return _quantity; }
set
{
if (value == _quantity) return;
_quantity= value;
CalculateExtendedPrice();
}
}
public decimal ExtendedPrice { get; set; }
public virtual Product Product { get; set; }
public virtual SalesOrder SalesOrder { get; set; }
private void CalculateExtendedPrice()
{
ExtendedPrice = UnitPrice * Quantity;
}
}
If Code First is not an option, what about making your entity a partial class (if it is not already) and putting your business logic in a separate code file (but with the same class name). This way, your main code file will get overwritten when you generate, but your secondary code file will remain. This is the usual way to deal with generated code.
I have two database classes as defined below:
public class TopDate
{
[Key]
public int DateId { get; set; }
public DateTime Date { get; set; }
}
public class TopSong
{
[Key]
public int SongId { get; set; }
public string Title { get; set; }
public int DateId { get; set; }
}
where DateId is foreign key to TopSong
I am creating a controller through which i can create, delete or edit these database values.
When i right click on controller class and add controller i can only select one of the two classes defined above. Is there a way to make 1 controller to handle database updates to both these tables on one page?
Error Image:
Your controller should not be dealing directly with domain objects (meaning those things that are directly associated with your database). Create a ViewModel that contains the properties that you need, use your service layer to populate the ViewModel and your controller will use that as the Model for its base. An example of your ViewModel could be something like the following given your description above:
public class MusicViewModel
{
public int SongId {get;set;}
public string Title {get;set;}
public IEnumerable<DateTime> TopDates {get;set;}
}
This view model would contain a list of all dates that a specific song was a Top Song.
The objects you showing (code) are database classes (so called domain objects).
What you need to do is to define a view model, a standard ASP MVC practice:
you define a class, that is tailored for specific view and only containing data relevant to that particular view. So you will have a view model for a view that will create a song, another that will update it etc.
Actually situation you describing is classical situation to use view models. Using domain objects in the views, however, is really really bad practice and prone to more problems than you want to deal with.
Hope this helps.
I am trying to dig into ASP.NET MVC 3, using the standard tutorials in the web, and I encounter a strage problem.
Currently, I am following the samples in a book, using a "Movie" class with movie genres stored in a separate entity, connected with a foreign key (okay, I am from Germany, so my class is named in German). I show only the relevant properties here. It's a database first approach using DbContext, my model was created from the edmx by using the EF 4.x DbContext Generator and the edmx was automatically created from the data base.
public partial class Film
{
public Film() { }
public int ID { get; set; }
public string Titel { get; set; }
public int GenreID { get; set; }
public virtual Genre Genre { get; set; }
}
public partial class Genre
{
public Genre() { }
public int GenreID { get; set; }
public string Name { get; set; }
}
When I create a new Controller with CRUD Views for the Film class, using a DBContext that provides a DBSet, I get an Edit view that uses a DropdownList to edit GenreID, labelled "Genre". Fine. That's what I want.
But then, I tried to create another edit view, separately. So I right-clicked into my Edit Action-Method, selected "Add View", called it "Edit2", used Film as model and "Edit" as scaffold template. In this view, I got a simple "EditorFor(m->m.GenreID)", labelled GenreID. That's not what I want.
Of course, I can change that manually. Of course, I can download a slew of scaffolding tools that claim to do better.
But I want to understand if this is a bug in the EF templates, or if my model is built wrong so that Genre / GenreID gets confused. When I create everything at once, scaffolding creates a DropDown, so there must be "just" some detail that's missing.
You will need to call your Action in your controller "Edit2".
I'm building a forum project for ASP.NET MVC 3, running on .NET 4 with the latest version of Entity Framework.
I have the usual forum design, with a Board with Categories, and Categories with Forums, Forums with Topics and Topics with Posts etc.
Simplified:
public class Category {
[Required]
public virtual Board Board { get; set; }
}
public class Forum {
[Required]
public virtual Category Category { get; set; }
}
public class Topic {
[Required]
public virtual Forum Forum { get; set; }
}
public class Post {
[Required]
public virtual Topic Topic { get; set; }
}
When a new post is created the topic is informed, and when a topic is changed, the forum is informed.
So, again simplified:
public class Forum {
public void TopicChanged(Topic topic) {
// Do stuff
}
}
public class Topic {
public void PostAdded(Post post) {
// Do stuff
this.Forum.TopicChanged(this);
}
}
So after creating a new Post (and committing it to the database), I call PostAdded on the parent topic. Now this is where it get odd!
When I commit the changes to my repositories, I get a validation error, Category on Forum is required.
If I look in the database, the Forum has a reference to the parent Category. If I stop the code and looks at the Forum object, it has a Category instance. So this looks like an issue with lazy loading, especially because if I add this line:
var cat = this.Category
At the bottom of the TopicChanged method in the Forum class, there's no longer any errors.
Am I doing something totally wrong here, have I run into a borderline issue, or what is going on? I figured EF would see that the reference is a lazy loaded reference, and if it hasn't been changed, there's no reason why this should fail on save???
Thanks,
Steen
I've fixed my problem. It might not be a really nice and clean solution, but at least I can handle this situation now, without having to change a lot of my code (which needs to run with nHibernate also). So no dirty solution.
Just to give you an idea on how it's solved, I'll try and explain it here.
On the Commit() method on my repository, I start off calling GetValidationErrors() on the DbContext instance. This returns the error I encountered above along with the entity where the error occurs. On the base type of this entity (the entity is a proxy generated by EF) I run through all properties and when I encounter a property with the Required attribute, I call GetValue on the identical property on the proxy object.
Enough talk, more code:
var errors = this.context.GetValidationErrors();
foreach (DbEntityValidationResult result in errors) {
Type baseType = result.Entry.Entity.GetType().BaseType;
foreach (PropertyInfo property in result.Entry.Entity.GetType().GetProperties()) {
if (baseType.GetProperty(property.Name).GetCustomAttributes(typeof(RequiredAttribute), true).Any()) {
property.GetValue(result.Entry.Entity, null);
}
}
}
Is it possible to use the selfvalidation attribute with my validations located in a metadatatype? I'm using Enterprise Library 5's Validation Application Block.
As I explained in my other answer, this isn't supported out of the box. However, this can be achieved by hooking into the framework using depedency injection and replace the existing AttributeValidatorFactory implementation. I written a post on my weblog on how to do this: Mixing Validation Application Block With DataAnnotation: What About SelfValidation?
I hope this helps.
This is currently not supported (out of the box) by VAB. Look for instance at this thread at the EntLib forum. I think the main reason this is not supported is because you can't simply place the [SelfValidation] method on the meta data type and expect this to work. Reason it won't work is because self validation methods will typically validate instance members of the type. The signature of the self validation method does not contain the actual object to validate.
A simple work around is call into the meta data type from the entity. For instance:
[MetadataType(typeof(InvoiceMetaData))]
[HasSelfValidation]
public partial class Invoice
{
public string Name{ get; set; }
public int Price { get; set; }
[SelfValidation]
public void CustomValidate(ValidationResults results)
{
// Call into the meta data class
InvoiceMetaData.Validate(this, results);
}
}
public class InvoiceMetaData
{
[StringLengthValidator(1, 10, Tag = "Name")]
string Name { get; set; }
[RangeValidator(0, RangeBoundaryType.Inclusive, 0,
RangeBoundaryType.Ignore, Tag = "Price")]
int Price { get; set; }
public static void CustomValidate(Invoice instance,
ValidationResults results)
{
results.AddResult(new ValidationResult("ErrorMessage1",
instance, "", "", null));
}
}
This of course isn't a very clean solution. VAB however is very extendable and version 5.0 only got better. If you want you can swap existing AttributeValidationFactory and replace it with a version that is able to do this. It won't be easy though.
Cheers