I'm working on an MVC3 application.
I created my POCO classes through the ADO.NET DbContext Generator and
I'm using partial classes to add validation on properties.
Now, when I try to serialize one of my entities I receive this error:
"Cannot serialize member .... of type
'System.Collections.Generic.ICollection`1[....."
I googled this error and I discovered that it's possible to add the tag
[XmlIgnore] to certain properties.
But the point is that I can't put this tag on the properties because they are
created everytime by the generator.
So how I can do this in a simpler way ?
The key is the MetadataTypeAttribute. You can add this to your partial class which implements the additional properties and your validation logic. Then create a meta data class with a property of the same name of your generated class, and apply the attribute you need.
[MetadataType(typeof(MyPOCOMetaData))]
public partial class MyPOCO
{
// your partial validation code and properties
}
public class MyPOCOMetaData
{
[XmlIgnore]
public string GenerateProperyName { get; set; }
}
Related
I'm new to MVC and the EF. My app is a simple code-first with several POCO classes and a DBContext like this:
public class ExpDefContext : DbContext
{
public DbSet<Experiment> Experiments { get; set; }
public DbSet<Research> Researches { get; set; }
...
The problem: I need to add to my data model an entity-set that its type is built at runtime from user input, meaning I have no idea of its data structure.
I read the non-generic Dbset class is made just for this, so I added to the context:
public DbSet Log { get; set; }
...and created a constructor for the context that accepts the runtime-type and sets the new Dbset:
public ExpDefContext(Type LogRecType)
{
Log = Set(LogRecType);
}
(the type by the way is built using Reflection.Emit).
In the controller I create the type (named LogRec) and pass it to a new DBContext instance. Then I create a LogRec instance and try to Add it to the database:
Type LogRec;
LogRec = LogTypeBuilder.Build(dbExpDef, _experimentID);
var dbLog = new ExpDefContext(LogRec);
var testRec = LogRec.GetConstructor(Type.EmptyTypes).Invoke(Type.EmptyTypes);
dbLog.Log.Add(testRec);
dbLog.SaveChanges();
and I get an exception from the dbLog.Log.Add(testRec):
The entity type LogRec is not part of the model for the current context
What am I doing wrong?
Is there a better way to do this (preferably without diving too deep into the Entity Framework)?
Thanks
I suspect that EF only reflects over the generic DbSet<T> properties in your derived DbContext and ignores any non-generic DbSet properties when the model is created in memory.
However, an alternative approach might be to use the Fluent API in OnModelCreating to add your dynamic type as an entity to the model.
First of all you can add a type to the model only when the model is built in memory for the first time your AppDomain is loaded. (A model is built only once per AppDomain.) If you had a default constructor of the context in addition to the overloaded constructor and had created and used a context instance using this default constructor your model would have been built with only the static types and you can't use the dynamic type as entity anymore as long as the AppDomain lives. It would result in exactly the exception you have.
Another point to consider is the creation of the database schema. If your type is unknown at compile time the database schema is unknown at compile time. If the model changes due to a new type on the next run of your application you will need to update the database schema somehow, either by recreating the database from scratch or by defining a custom database initializer that only deletes the LogRec table and creates a new table according to the new layout of the LogRec type. Or maybe Code-First Migrations might help.
About the possible solution with Fluent API:
Remove the DbSet and add a Type member instead to the context and override OnModelCreating:
public class ExpDefContext : DbContext
{
private readonly Type _logRecType;
public ExpDefContext(Type LogRecType)
{
_logRecType = LogRecType;
}
public DbSet<Experiment> Experiments { get; set; }
public DbSet<Research> Researches { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
var entityMethod = typeof(DbModelBuilder).GetMethod("Entity");
entityMethod.MakeGenericMethod(_logRecType)
.Invoke(modelBuilder, new object[] { });
}
}
DbModelBuilder doesn't have a non-generic Entity method, hence dynamic invocation of the generic Entity<T> method is necessary.
The above code in OnModelCreating is the dynamic counterpart of...
modelBuilder.Entity<LogRec>();
...which would be used with a static LogRec type and that just makes the type as entity known to EF. It is exactly the same as adding a DbSet<LogRec> property to the context class.
You should be able to access the entity set of the dynamic entity by using...
context.Set(LogRecType)
...which will return a non-generic DbSet.
I have no clue if that will work and didn't test it but the idea is from Rowan Miller, member of the EF team, so I have some hope it will.
Is there a different way of setting the [AllowHtml] attribute on a property of a class that is being auto-generated by EntityFramework? I hate changing the autogenerated files because every time I make a change to the model, my changes get lost.
But there is no other obvious way for setting [AllowHtml] for a specific property other than by using the attribute. Is there a non-attribute way of doing it?
You can use the MetadataTypeAttribute to specify attributes for the generated code in an associated (buddy) class. So you put your attributes in a separate class which won't be effected with the code re-generation:
[MetadataType(typeof(YourEntityMetadata))]
public partial class YourEntityClass
{
}
public class YourEntityMetadata
{
[AllowHtml]
public string YourPropertyWithHtml { get; set; }
}
The property names in the Metadata class should match your entity property names.
I am working on an mvc3 application and having some problems with getting validation to work as I want.
The application is using buddy classes for the models. (This is something I haven't used in the past and I am a little confused why they are used...anyway)
I want to add required fields to ensure data been submitted is correct. I have tried adding the required field to the buddy class.
When I submit the form no client-side validation takes place and the debugger steps into the entity frameworks generated code. Here is complains that the fields that contain null values are causing are invalid. If I step through all of those it finally gets to the controller where my if (ModelState.IsValid) is showing false.
I have client-side validation switched on.
Am I meant to be applying the data validation at the buddy class level or at the view model?
One other question is why use buddy classes? to me they seem to over complicate things.
Updated added an example of the buddy class
[MetadataType(typeof (CustomerMetaData))]
public partial class Customer
{
public string Priorty
{
get
{
var desc = (Priority) Priority;
return desc.ToString().Replace('_', ' ');
}
}
internal class CustomerMetaData
{
[Required]
[DisplayName("Priorty")]
public string Priorty { get; set; }
Buddy classes are metadata classes to put data annotation attributes when you are not in control of the original class i.e. can't edit it. Typical situation is when the class is generated by an ORM like Entity Framework.
//Can't edit this class
public partial class YourClass{
public string SomeField {get; set;}
}
//Add a partial class
[MetadataType(typeof(YourClassMetadata))]
public partial class YourClass{
}
//And a metadata class
public class YourClassMetadata
{
[Required(ErrorMessage = "Some Field is required")]
public string SomeField {get; set;}
}
are you sure that you have [MetadataType(typeof(YourClassMetadata))]?
More about buddy classes here and here
You would typically use a buddy class when it isn't possible to add meta data to an entity class such as when a model is automatically generated by an ORM tool. In this case any meta data you had applied would be lost.
Therefore, your original (automatically generated) class would be defined as a partial class:
public partial class Customer
{
public string Priority { get; set; }
}
And then you would generate your buddy classes to add the meta data.
[MetadataType(typeof(CustomerMetaData))]
public partial class Customer
{
}
internal class CustomerMetaData
{
[Required]
public string Priority { get; set; }
}
You would then pass the Customer class to the view where the Priority would be set.
In your case i'm not sure if you only have one partial class or two (as the other is not shown but please provide if there is). I'm interested to know how you obtain the priority information from the customer as i'm wondering if this is an issue with how you use ModelState.IsValid? The reason I ask is that no set accessor is declared on the Priority property so i'm wondering how this is set from the view in order to report that it is not valid?
You would also use a buddy class when it isn't possible to add meta data to an entity class such as when a model is automatically generated by an WCF Data Contract.
I used LINQ to SQL to generate a dbml file which contains the database model for my database table. I want to use UIHint to let MVC present some fields as DropDownLists or Checkboxes in edit mode. But if I change the file, it will be lost if it's been regenerated. How should I solve that issue? I'm quite new to MVC and still learning. I've set up a controller with views for all CRUD elements, but now I'm finetuning and I'm running into this problem.
Since Linq-to-SQL auto-generates partial classes, you'll need to create a partial 'buddy class' where you will add your Data Annotations. Your buddy class mirrors portions of the auto-generated class that you need to modify. You tie them together with [MetadataType(typeof(BuddyClassName))] The partial buddy class and the auto-generated partial class will be merged together when you compile your project.
In an example given that:
Your namespace is "Project.Models"
Your Linq-To-Sql class is called "Products"
using System.ComponentModel.DataAnnotations;
namespace Project.Models
{
[MetadataType(typeof(ProductsMeta))]
public partial class Products
{
// You can extend the products class here if desired.
public class ProductsMeta
{
// This is a Linq-to-Sql Buddy Class
// In here you can add DataAnnotations to the auto-generated partial class
[Key]
public int ProductKey { get; set; }
[Display (Name = "Product Name")]
[Required(ErrorMessage = "Product Name Required")]
[StringLength(255, ErrorMessage = "Must be under 255 characters")]
public string ProductName { get; set; }
[UIHint("MultilineText")]
public string Description { get; set; }
}
}
}
These articles were very helpful:
ScottGu: ASP.NET MVC 2: Model Validation
How to: Validate Model Data Using DataAnnotations Attributes
Validating with Data Annotation Validators
If you are going to use the entities directly you should create a partial class and add your annotations there. This way when the model is regenerated you will not lose your annotations.
Castle Validator uses attributes to specify validation rules. How can you hook these up with Subsonic's generated classes (or any classes where you can't define the attributes on)? Is there a way to programatically specify validation rules without using the attribute method?
I think the best way to do that is using MetadataType.
It's a DataAnnotations that let's your class have like a pair or something like that. I don't know how to explain it better so, let's for the samples:
You first need to add this directive to your code:
using System.ComponentModel.DataAnnotations;
Them you should create the partial class of you generated class with an attribute specifying that this class has an MetadataType:
[MetadataType(typeof(UserMetadata))]
public partial class User
{
}
Then you create your metadata class with your castle validation:
public class UserMetadata
{
[ValidateNonEmpty]
[ValidateLength(6, 24)]
public string Username { get; set; }
[ValidateNonEmpty]
[ValidateLength(6, 100)]
[ValidateEmail]
public string Email { get; set; }
[ValidateNonEmpty]
[ValidateLength(6, 24)]
public string Password { get; set; }
}
There are a few ways to do this - attributes is the lowest friction option, but obviously doesn't deal well with generated code or validation of multiple properties better expressed in code.
Take a look at the following link for some indications on how to do this blog post: Castle Validator Enhancements
If you have a look at the castle source code these are some good starting points:
IValidationContributor interface
DefaultValidationPerformer class