How to Add Data Annotations to Entity Framework Generated Classes?

Add Annotations to Entity Framework Generated Class

Entity Framework automatically generates classes based on database tables. If you need to add data annotations to a generated class, you can't simply modify the existing class as it will be overwritten upon regeneration.

Solution: Custom Metadata Class

Fortunately, generated classes are always partial classes, allowing you to define a separate partial class with the desired annotations.

For example, let's say we have a generated class named ItemRequest. Create a new partial class with the following structure:

using System.ComponentModel;
using System.ComponentModel.DataAnnotations;

namespace [YourNamespace]
{
    [MetadataType(typeof(ItemRequestMetaData))]
    public partial class ItemRequest
    {
    }

    public class ItemRequestMetaData
    {
        [Required]
        public int RequestId { get; set; }

        //... (Additional annotations can be added here)
    }
}

This ItemRequestMetaData class becomes the metadata store for additional annotations. By specifying the [MetadataType] attribute on the ItemRequest partial class, EF will automatically map these annotations to the base ItemRequest class, marking the required field as non-nullable.

The above is the detailed content of How to Add Data Annotations to Entity Framework Generated Classes?. For more information, please follow other related articles on the PHP Chinese website!