Ignoring a class property in Entity Framework 4.1 Code First

.net, c#, ef-code-first, entity-framework, entity-framework-4.1

Solution

You can use the `NotMapped` attribute data annotation to instruct Code-First to exclude a particular property

public class Customer
{
    public int CustomerID { set; get; }
    public string FirstName { set; get; } 
    public string LastName{ set; get; } 
    [NotMapped]
    public int Age { set; get; }
}

`[NotMapped]` attribute is included in the `System.ComponentModel.DataAnnotations `namespace.

You can alternatively do this with `Fluent API` overriding `OnModelCreating` function in your `DBContext` class:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
   modelBuilder.Entity<Customer>().Ignore(t => t.LastName);
   base.OnModelCreating(modelBuilder);
}

http://msdn.microsoft.com/en-us/library/hh295847(v=vs.103).aspx

The version I checked is `EF 4.3`, which is the latest stable version available when you use NuGet.

Edit : SEP 2017

Asp.NET Core(2.0)

Data annotation

If you are using asp.net core (2.0 at the time of this writing), The `[NotMapped]` attribute can be used on the property level.

public class Customer
{
    public int Id { set; get; }
    public string FirstName { set; get; } 
    public string LastName { set; get; } 
    [NotMapped]
    public int FullName { set; get; }
}

Fluent API

public class SchoolContext : DbContext
{
    public SchoolContext(DbContextOptions<SchoolContext> options) : base(options)
    {
    }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Customer>().Ignore(t => t.FullName);
        base.OnModelCreating(modelBuilder);
    }
    public DbSet<Customer> Customers { get; set; }
}

Problem

My understanding is that the `[NotMapped]` attribute is not available until EF 5 which is currently in CTP so we cannot use it in production. How can I mark properties in EF 4.1 to be ignored? UPDATE: I noticed something else strange. I got the `[NotMapped]` attribute to work but for some reason, EF 4.1 still creates a column named Disposed in the database even though the `public bool Disposed { get; private set; }` is marked with `[NotMapped]`. The class implements `IDisposeable` of course but I don't see how that should matter. Any thoughts?

Original source

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