I am starting MVC4 with VS2012. I am also using EF5 with the "Database First" method of creating my classes.
However because the generated glasses can be regenerated I cannot put the Data Annotation details to assist with validation.
I have seen some code snippets that use MetaData and partial classes but I was wondering if anyone knows of a small compilable example that I can look at and pull apart to better understand how the vasious classes interlink.
Many many thanks for any help.
Dave
You can achieve what you need through extending models. Suppose that EF generated the following entity class for you:
namespace YourSolution
{
using System;
using System.Collections.Generic;
public partial class News
{
public int ID { get; set; }
public string Title { get; set; }
public int UserID { get; set; }
public virtual UserProfile User{ get; set; }
}
}
and you want do some work arounds to preserve your you data annotations and attributes. So, follow these steps:
First, add two classes some where (wherever you want, but it's better to be in Models) like the following:
namespace YourSolution
{
[MetadataType(typeof(NewsAttribs))]
public partial class News
{
// leave it empty.
}
public class NewsAttribs
{
// Your attribs will come here.
}
}
then add what properties and attributes you want to the second class - NewsAttribs here. :
public class NewsAttrib
{
[Display(Name = "News title")]
[Required(ErrorMessage = "Please enter the news title.")]
public string Title { get; set; }
// and other properties you want...
}
Notes:
1) The namespace of the generated entity class and your classes must be the same - here YourSolution.
2) your first class must be partial and its name must be the same as EF generated class.
Go through this and your attribs never been lost again ...
Related
In Entity Framework 6, given class A and derived class B: A, I would like to load entities A into instances of B without having to code for each property.
So given:
public class A
{
public Guid AId { get; set; }
public string Value { get; set; }
}
public class B: A
{
[NotMapped]
public string OtherValue { get; set; }
}
public MyDbContext: DbContext
{
public DbSet<A> As { get; set; }
}
I would like to:
using (MyDbContext db = new MyDbContext())
{
IEnumerable<B> Bs = db.As.LoadBsSomehow()
}
I'm guessing I could add DbSet<B> Bs { get; set; } and then in OnModelCreate I could override the table name to As perhaps. I'd like to avoid that if I can.
The purpose of doing this is that we need view models that need the underlying model plus some other properties and I don't want to mess up the models with all the different view model properties. This would simplify coding and maintenance for when the main model is changed -- the inheritance would automatically handle the changes in the derived class (view models).
I can then set the additional properties of the Bs in a Select or other method.
Also, I do NOT want to use reflection. I can code that up if I need it. I'd rather find out if EF 6 has the ability to do this natively.
UPDATE: I can do DbContext.Database.SqlQuery<T>. I would prefer to be able to use LINQ instead of writing SQL. I have no problem writing SQL, but LINQ is much more maintainable from a code perspective. Perhaps if I can use LINQ to create an IQueryable<B> and get the SQL for it?
I am using MVC 4.0 and entity-framework 5 to generate model.
I m trying to understand concept of customization, i followed same steps given in tutorials site like this and this
only difference is I am adding this customization class code in different sub folder because when directly try to add this in model folder it shows error employee class already created in this ( autogenrated by entity framwork)
Auto generated code By Entity Framework
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated from a template.
//
// Manual changes to this file may cause unexpected behavior in your application.
// Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
namespace CustomizationConceptUmang.Models
{
using System;
using System.Collections.Generic;
public partial class employee
{
public int id { get; set; }
public string name { get; set; }
public string email { get; set; }
}
}
Code for customization
namespace CustomizationConceptUmang.Models.ViewModel
{
[MetadataType(typeof(employeeMetaData))]
public partial class employee
{
}
public class employeeMetaData
{
[Display(Name="Employee Name")]
public string name { get; set; }
}
}
View
<th>
#Html.DisplayNameFor(model => model.name)
</th>
Still it showing name instead of Employee Name
please suggest me how to resolve this Thanks in advance.
The partials are in different namespaces, so they're two separate classes and the metadata is not applied to the employee entity.
Match up the namespace to combine multiple partial classes into one.
Anyway don't use Entity Framework models as viewmodels. Create a separate class with annotations for a viewmodel, and map to and from your entity. You'll thank me later.
I am trying to create a RESTful web service that returns a list of products using ASP.NET MVC4 Web API. Here is my controller class
public class ProductController : ApiController
{
public IEnumerable<Product> GetProducts()
{
WebCatalogContext dbcontext = DatabaseConfig.Instance.Context;
List<Product> plist = dbcontext.Products.ToList();
return plist;
}
}
When I run my service and call the following URL from my browser :/api/Product, I get System.Runtime.Serialization.SerializationException. I looked into my plist object and there is no problem with it.
Here is my data model:
[DataContract(Name = "p")]
[Serializable]
public class Product
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[DataMember(Name = "id")]
public int Id { get; set; }
[Required, MaxLength(50)]
[DataMember(Name = "ti")]
public string Title { get; set; }
[Required]
[DataMember(Name = "de")]
public string Description { get; set; }
[Required]
[DataMember(Name = "ph")]
public string PhotoURL { get; set; }
[DataMember(Name = "ca")]
public virtual ProductCategory Category { get; set; }
}
[DataContract(Name="pc")]
[Serializable]
public class ProductCategory
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[DataMember(Name="id")]
public int Id { get; set; }
[DataMember(Name="nm")]
public string Name { get; set; }
}
When I remove the reference to ProductCategory from my Product class, all things work just fine. But, when I include it I get the following exception.
Type 'System.Data.Entity.DynamicProxies.Product_664E9A0AA1F165A26C342B508BFFF1279FD3FE059285225BDA19F407A29A9CAD' with data contract name 'Product_664E9A0AA1F165A26C342B508BFFF1279FD3FE059285225BDA19F407A29A9CAD:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.
Any idea about what I am missing?
Regards
Entity Framework has wrapped your POCO with an EF Proxy POCO so it can perform lazy loading - this uses the Virtual attribute to create a 'lazy-loadable' navigation property. I expect that is where the serialization error comes from.
You could make a new class and map the POCO to that - then pass the DTO style class from the controller. I've never returned an EF object directly from the API (I always map to some something else) so I don't know another option.
EF POCO to DTO (data transfer object) is relatively painless if you use a tool like http://valueinjecter.codeplex.com/ or http://automapper.org/
To support Lazy Loading for navigation properties which is declared as virtual, EF will generate the proxies for any models which have navigation properties which leads to this kind of exception.
For very simple application, you can use model from EF as DTOs (if having no navigation properties), but for complex application, you should do separate and differ between DTOs and domain models. It should not be mapping 1:1 between DTO and domain model.
Therefore, in your case, you create more DTO model for Web API layer, it will be fine.
A little new to EF, so please bear with me if the answer to this is obvious. I'm doing a tutorial that uses EF, and two DbSets are defined like this:
public DbSet<BrokerageAccount> BrokerageAccounts { get; set; }
public DbSet<Customer> Customers { get; set; }
The customer class looks like this-- it's a POCO (some code cut for brevity):
public class Customer
{
public Customer()
{
BrokerageAccounts = new HashSet<BrokerageAccount>();
}
// Primitive properties
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
// Navigation properties
public ICollection<BrokerageAccount> BrokerageAccounts { get; set; }
}
}
The BrokerageAccount class is a POCO as well, very similar in design to Customer.
So far so good. The code I have a question about is below. There is an association made in the main program between Customer and BrokerageAccount that I don't follow. The code reads like this:
public Customer GetCustomer(string custId)
{
using (var context = DataContext)
{
return context.Customers
.Include("BrokerageAccounts").SingleOrDefault(c => c.CustomerCode == custId);
}
}
I can't figure out how the association/join is made between Customer and BrokerageAccount. I don't see any config or other files in my VS 2010 project that tells what associates the two DbSets, what foreign key column to use, etc.
Perhaps I'm missing something obvious or a mapping file of some sort, but just because Customer has an ICollection of BrokerageAccount along with a comment above that says "Navigation Properties", doesn't make it so. In EF, how are those associations established?
The normal way of setting up the navigation properties is to use the ModelBuilder, This gives you a fluent api to set up the associations, take a look at this for some in depth stuff about how you go about this.
http://xhalent.wordpress.com/2011/01/21/configuring-entity-framework-4-codefirst/
Entity framework will guess at what you meant if you dont set up the nav properties manually, in the above case it will probably set up your nav properties as expected as you only have a single 1-* relationship between customer and BrokerageAccount which appears to be named sensibly.
There is also an attribute method that you can use to set up the navigation properties.
Using MVC3 and Entity Framework.
Am trying to get validation flowing from data model
Question: On an entity framework save, how can I automatically put in the [MetadataType tag below for my buddy class?
[EdmEntityTypeAttribute(NamespaceName="ModelValidationTestModel", Name="Person")]
[Serializable()]
[DataContractAttribute(IsReference=true)]
[MetadataType(typeof(Person_Validation))] // I want EF to put this line in automatically
public partial class Person : EntityObject
...
[Bind(Exclude="PersonID")]
public class Person_Validation
{
[Required]
public string FirstName { get; set; }
[Required]
public string LastName { get; set; }
[Required]
public int Age { get; set; }
[Required]
public string Email { get; set; }
}
Using example from: http://weblogs.asp.net/scottgu/archive/2010/01/15/asp-net-mvc-2-model-validation.aspx
I think the best option is not to mess with the class generated by EF. Instead define your own partial class:
[MetadataType(typeof(Person_Validation))]
public partial class Person
{
//rest of class may be empty
}
You can do this in the same file as the Person_Validation class if you like.
It's not automatic, but it is safe (your changes won't get lost). This approach will work with any code generation framework (that uses partial classes), not just EF.
Data Annotations/attributes are baked at compile time and you cannot add them dynamically. I would recommend you to avoid passing/getting your EF models to/from the views. You should be using view models which are classes specifically tailored to the needs of a given view. It is those view models that will handle the would handle view specific validations such required, format, ...). You could then use AutoMapper to have your controller map between your view models and the EF models.