I have an EF 5 entity called Account generated with the standard template.
It has a property AccountTypeId.
When it changes, I need a notification so another field can be updated.
How is this typically done? This is needed for only one property, so I don't want to use a modified template.
AccountTypeId is bound to a ComboBox in the UI in WinForms, so it's not really an MVVM app as I would normally do in WPF.
One way is to go to the EDMX and rename the field to AccountTypeID_Internal (for example), and in the EDMX set the property to Private. Then create a Partial Class.
Generated Account.cs should look like:
//------------------------------------------------------------------------------
// <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 <yournamespace>
{
using System;
using System.Collections.Generic;
public partial class Account
{
private int AccountTypeId_Internal { get; set; }
// other auto generated properties
}
}
Account.Partial.Cs
public partial class Account : INotifyPropertyChanged
{
public Int AccountTypeId
{
get
{
return this.AccountTypeId_Internal;
}
set
{
this.AccountTypeId_Internal = value;
// Do INotifyPropertyChangedLogic
}
}
// Implement INotifyPropertyChanged
}
The advantage of this is that your already written code doesn't have to change at all. The downside is that if you remove the Accout from the edmx and re-add it you will have to go through the edmx steps again.
You can do this with a few lines of code using a NuGet package called PropertyChanged.Fody. The package documentation is on GitHub. See my CodeProject tip "Adding INotifyPropertyChanged to Entity Framework Classes".
I should point out that that technique will implement INPC for every property in the class. If you only want INPC for a single property and you don't want to modify the T4 template or EDMX file then you could leverage the fact that the entity classes are generated with the "partial" keyword, allowing you to add a "wrapper" property in a separate (non-generated) file like Erik Philips described. You would have to modify your existing code to reference the wrapper property but nothing would break when you re-generate the model or entities.
Related
Entity Framework 7 reverse engineering tool does not generate the POCOs as partials. Is there a specific reason for that?
Before EF7 we used to get partial classes so I could extend the functionality of POCOs. I was using partial classes to map the Id property to the Primary key property as shown below;
public partial class User: EntityBase
{
public override int Id
{
get { return UserId; }
set { UserId= value; }
}
}
How can I do that in EF7?
Thank you.
It was just an oversight. An Entity Framework bug was raised on this (see https://github.com/aspnet/EntityFramework/issues/3428). It was fixed today (Oct 16, 2015) - and will be in tonight's nightly build.
As a workaround the scaffold-templates approach mentioned above should work for now.
Or you are also free to just manually search and replace to add the word partial into any POCO class once it has been generated (though it would get overwritten every time you generated them again).
dnx ef dbcontext scaffold-templates EntityFramework.SqlServer
scaffold-templates command can be used to generate the EntityFramework.SqlServer.Design.DbContextTemplate.cshtml and EntityFramework.SqlServer.Design.EntityTypeTemplate.cshtml template files in the project directory to be used during scaffolding.
EntityTypeTemplate customization example to add partial class support:
....
....
#:namespace #Model.Namespace
#:{
#: public partial class #Model.EntityType.Name
#: {...
....
....
....
I am using 6.1.3 and models are generated as partials.
I have existing .net 4 application which is based on object context.
Now I'm adding DbContext in to existing application by inheriting DbContext and call constructor method and pass the existing object context. i.e.
public class DemoModelEntitiesDbContext : DbContext
{
public DemoModelEntitiesDbContext():base(new DemoModelEntities(), dbContextOwnsObjectContext:true)
{
}
public DbSet<ELMAH_Error> ELMAH_Error { get; set; }
}
Than When I call,
using (DemoModelEntitiesDbContext context = new DemoModelEntitiesDbContext())
{
foreach (ELMAH_Error entity in context.ELMAH_Error.ToList())
{
Console.WriteLine(entity.ID);
}
}
I am getting following error message,
"The type 'ObjectContextDemo.ELMAH_Error' was not mapped. Check that the type has not been explicitly excluded by using the Ignore method or NotMappedAttribute data annotation. Verify that the type was defined as a class, is not primitive, nested or generic, and does not inherit from EntityObject."
I checked my existing entities are inheriting from EntityObject.
How to add DbContext in to existing application and not changing existing code?
You could cast to object context but then you gain nothing from DbContext if you 100% stick with existing code. but Ive done that with POCOs, not EntityObjects and can't confirm that it would work with entityobjects.
Otherwise it's not possible to do that without changes. DbContext does not support EntityObject. DbContext is designed for POCOs. Plus there are other code differences between DbContext and ObjectContext. You'd have to change even if you were already using POCOs. If you are using the EF designer, you'd have to start by using a different code gen template (ef5 DbContext template). But that will result in very different classes and plenty of changes to your EF calls in your app.
I am playing around building some buildingblocks based on database tables.
So I've created an UsersManager and a ValidationManager both based on the EDMX "templates".
I'd really like to loose couple those two components with MEF. But therefore i need to create Interfaces of the entityobjects exposed in the ValidationManager.
Is there an easy way of creating those Interfaces, in that manner i can still use the EDMX generated classes?
Thanx,
Paul
Using an example of a database with a Product Table, is this what you're trying to achieve....
but still use generated entity classes (using either the standard EF generator or another POCO generator of some sort).
I'm not sure - as you mention MEF and I don't see it being directly related.
The generated entity classes are partial classes which will allow you to extend the generated class which in this case you want to extend to implement an interface.
Presuming the following interface is going to be used to introduce the layer of abstraction...
public interface IEntity {
public bool IsDeleted { get; set; }
}
Create a new class file with and extended Product class...
public partial class Product : IEntity {
public bool IsDeleted {
get {
throw new NotImplementedException();
}
set {
throw new NotImplementedException();
}
}
}
You have now extended your generated entity Product with the partial class custom code - and you can use it as normal through EF.
Now instead of your UserManager and ValidationManager classes having a hard reference to Product, instead they'll only have reference to IEntity.
If I didn't understand the question, please provide more details on exactly it is you want to do.
Using EF with Winforms in C#. I’d like to add full custom properties to our entities, using partial classes. All entities already have partial classes with validation stuff and some more so I’d just add the properties that I need. By full property I mean property with getter and setter so not just a computed/readonly property. I want to this mostly to get around working directly with some DB mapped properties which are badly designed or have other problems.
For example, one case would be like this:
// entity class, generated
public partial class Customer
{
public string Spot {get;set}
}
// partial class, manually changed
public partial class Customer
{
public int? xxxSpot
{ get { return Int32.Parse(Spot.Trim()); } // some code omitted
{ set { Spot = value.ToString().PadLeft(5); }
}
So my custom properties will be built around existing, DB mapped properties of the entity. I’d like to use these custom properties like normal ones, ie to bind them to UI controls and so on. I’ve tried one and so far it works great.
Is this a good idea? If not, why ? And what else should I consider when doing this?
You have answered your own question - it works and there is no reason why to not do that. If you want to improve design of your entities you can even try to change visibility of your mapped properties to ensure that other classes must use only your custom properties with additional logic.
I'm using entity framework designer to build entities. I found the designer really hard to use because it overwrite all your manually change after each model update using the designer. How did you round off this problem? Thanks!
What sorts of things are you manually changing? The entity still has to be mappable to the database schema.
You can extend or add functionality by declaring a partial class.
Don't make any change to the entities in the generated file -- I think it says that in the header.
All of the entities are generated as partial classes, which means you can declare "more" of the class elsewhere.
Here is an example:
public partial class Name
{
public string First { get; set; }
}
public partial class Name
{
public string Last { get; set; }
}
Although I have two different class declarations, potentially in different files and folders within the project, it gets compiled as one class.
I can now use the Name class like this:
var name = new Name();
name.First = "Jane";
name.Last = "Doe";
As you can see, the properties from both declarations are unified in an object of type Name.
To apply this to EF, leave the partial entity class alone, and declare a separate partial class with the same name to add functionality.
There is an alternative third-party tool. For more information, refer this. Currently, Devart Entity Developer doesn't include the Update From Database functionality. The Update From Database feature is on our roadmap.