How Can I Add Data Annotations to Entity Framework-Generated Classes Without Overwriting Them?

Creating Data Annotations for Entity Framework-Generated Classes

When working with Entity Framework, generated classes often lack necessary data annotations for validation. In situations like this, a safe way to define constraints is through a partial class.

For example, if you have the following generated class ItemRequest with fields like RequestId, you may want to mark certain fields as required:

public partial class ItemRequest
{
    public int RequestId { get; set; }
}

However, editing the generated class directly can result in your annotations being overwritten. Instead, create a second partial class with the desired annotations:

namespace MvcApplication1.Models 
{
    [MetadataType(typeof(ItemRequestMetaData))]
    public partial class ItemRequest
    {
    }

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

By using this approach, you ensure that your data annotations are preserved even after code generation updates.

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