How to work with Portable Class Library and EF Code-first?

问题

I'm doing an Windows Phone app where I have a WebApi running in Azure.

I'm using the new "Portable Class Library" (http://msdn.microsoft.com/en-us/library/gg597391.aspx) for my "Models" project which is of cause shared between my WebApi project (this is a normale ASp.NET MVC 4 project) and my Windows Phone project.

This works great and the model (POCO) classes are serialized and deserialized just as I want.

Now I want to start storing some of my Models/POCO objects and would like to use EF Code-first for that, but that's kind of a problem as I can't add the EntityFramework assembly to my "Portable Class Library" project, and really I would not like to either as I only need a small part (the attributes) in my Models project.

So, any suggestions to how a approach this the best way?

UPDATE: Well, it seems like I can actually add the EntityFramework assembly to the project, but that doesn't really help me, as the attributes I need to use lives in System.ComponentModel.DataAnnotations which can't be used on Windows Phone. Any suggestions still?

回答1:

Don't use attributes. Use fluent API instead and create separate assembly for persistence (EF) which will reference your model assembly. Persistence assembly will be use used by your WebAPI layer.

回答2:

I use a modified approach than Mikkel Hempel's, without the need to use pre processing directives.

Create a standard .NET class library, call it Models

Create a partial class representing what you want to be shared

public partial class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

For non-portable code (like DataAnnotations), create another partial class and use Metadata

[MetadataTypeAttribute(typeof(Person.Metadata))]
public partial class Person
{
    internal sealed class Metadata
    {
        private Metadata() { } // Metadata classes shouldn't be instantiated

        // Add metadata attributes to perform validation
        [Required]
        [StringLength(60)]
        public string Name;
    }
}

Create a Portable Class Library, and add the class from step 2 "As Link"

回答3:

When I need my domain-project across multiple platforms, I usually:

Create the standard .NET-class library project for the domain code
For each platform I create a platform specific class library
For each platform specific class library I add the files from the standard .NET-class library as links (Add existing files -> As link) and hence they're updated automatically when you edit either the linked file or the original file.
When I add a new file to the .NET-class library, I add it as links to the platform specific class libraries.
Platform specific attributes (i.e. Table and ForeignKey which is a part of the DataAnnotations-assembly) can be opted out using the pre-processor tags. Lets say I have a .NET-class library with a class and a Silverlight-project with the linked file, then I can include the .NET-specific attributes by doing:
```
#if !SILVERLIGHT
[Table("MyEntityFrameworkTable")]
#endif 
public class MyCrossPlatformClass 
{
    // Blah blah blah
}
```

and only include the DataAnnotations-assembly in the .NET-class library.

I know it's more work than using the Portable Class Library, but you can't opt out attributes in a PCL like in the example above, since you're only allowed to reference shared assemblies (which again DataAnnotations is not).

来源：https://stackoverflow.com/questions/11917736/how-to-work-with-portable-class-library-and-ef-code-first

标签

entity-framework-4.1

portable-class-library