Entity Framework Database First regeneration make me lose manual changes

Question

I'm making a website with MVC .NET. Since I'm an old school programmer who learn to design database first, I opted for the Database first approach. I'm also using "code generation" which create files with the extension `.tt` . Everything is working so far except one things that botters me. Classic scenario: - I realise that I am missing one field - I add the field in the database. - I go into the edmx and choose to update the model from the database. Then I go back to my code and things that use to work like special DisplayName tag that I put on top of model field were removed. For example if I have this: ``` public partial class Blog { public Blog() { this.BlogComments = new HashSet(); } public int IDBlog { get; set; } public string Title { get; set; } [AllowHtml] public string Content { get; set; } public System.DateTime DateCreated { get; set; } public string Author { get; set; } public virtual ICollection BlogComments { get; set; } } ``` It will become ``…

Accepted Answer

Don't edit the generated files. Ever. Just. Don't. Do. It.

Instead, make your edits in partial files in a different directory. To add attributes, declare a Metadata class at the top of your partial class definition.

```
[MetadataType(typeof(BlogMetadata))]
public partial class Blog
{
    // it's possible to add logic and non-mapped properties here
}
```

Now in your Metadata class, you can define attributes or other logic:

```
public class BlahMetadata
{
    [AllowHtml] 
    public string Content{ get; set; } 
}
```

Entity Framework Database First regeneration make me lose manual changes

Solution

Problem