How to Ignore Class Properties in Entity Framework Code First?

Ignoring a Class Property in Entity Framework 4.1 Code First

In Entity Framework (EF) 4.1, you may encounter the need to exclude certain properties from being included in the database schema. Fortunately, there are two approaches to achieve this.

[NotMapped] Attribute

This attribute is part of the System.ComponentModel.DataAnnotations namespace and can be applied to properties to indicate they should be ignored by EF.

[NotMapped]
public int Age { get; set; }

Fluent API

Alternatively, you can employ the Fluent API to override the OnModelCreating function within your DBContext class:

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

Additional Notes

• [NotMapped] works in EF versions 4.1 and later.
• The Fluent API approach is available in all versions of EF.
• Properties marked as [NotMapped] will not be mapped to columns in the database, even if they are part of an IDisposeable implementation.

Asp.NET Core (2.0)

For newer versions of EF, the approach is similar:

[NotMapped] Attribute

[NotMapped]
public int FullName { get; set; }

Fluent API

modelBuilder.Entity<Customer>().Ignore(t => t.FullName);

By using these techniques, you can effectively exclude properties from being mapped to the database, allowing for flexibility in your data modeling.

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