.NET Core / Blazor model attribute that doesn't get persisted to database

Question

I have a model in my Blazor app that I want to create a "transitory" attribute for. This attribute is used internally in the app, but I do not want to persist it to the database.

However, when I change my model, it seems that the build process wants to create a database migration and change the database structure, adding the new attribute.

Is there a way to add a non-persistent attribute to the model, that will be ignored for database writes, but can be populated when the model is being handled in the app?

Maybe the [NotMapped] attribute is what you are looking for? See also: exclude-or-ignore-property-of-an-entity-model-if-column-is-not-exist-in-database — topsail
– topsail, Commented Jun 2, 2024 at 14:38
This begs for an example. Too many ambiguities in the description. — Gert Arnold
– Gert Arnold, Commented Jun 2, 2024 at 17:58
@topsail NotMapped looks like exactly what I was looking for-- please submit as an answer and I'll accept it. Thanks — user101289
– user101289, Commented Jun 2, 2024 at 22:35

topsail · Accepted Answer · 2024-06-02 23:23:50Z

0

To create attributes on your models without worrying about EF Core automatically mapping the attributes to column in the DB or create migrations, you can annotate these attributes with the [NotMapped] annotation. This also works at the class level to mark the entire entity as not mapped to a DB table:

public class Foo
{
    public int Id { get; set; }
    public int SomeValue { get; set; }

    // Field will not be mapped to a DB Entity
    [NotMapped]
    public int Priority {get; set; }

    public DateTime CreatedOn { get; set; }
}

// Class will not be mapped to a DB Entity
[NotMapped]
public class Bar
{
    public int Id { get; set; }
    public int SomeValue { get; set; }
    public DateTime CreatedOn { get; set; }
}

See also: exclude-property-if-column-is-not-in-database and learnentityframeworkcore.com/notmapped

answered Jun 2, 2024 at 23:23

topsail

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