Entity Framework Core Customize Scaffolding

Question

I have done scaffolding of my SQLServer database. And it creates the POCO objects in the specified folder. What i would like to do is that it extends from my base class. I a

Answer 1

In my scenario I wanted to prefix all table names with an underscore. Version: Core 2.2.
I don't use Id as name of my primary key column, instead table name + Id like this: FoodId. This forced me to add the [Key] data annotation to the primary key.

Model
Scaffold Model Example:

using System;
using System.Collections.Generic;

namespace MyNamespace
{
    public partial class Food
    {
         public int FoodId { get; set; }
         public string Name { get; set; }
         public string Description { get; set; }
         public double Price { get; set; }
    }
}

Expected Result:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations; //Add

namespace MyNamespace
{
    public partial class _Food //Prefix with underscore
    {
         [Key] //Add
         public int FoodId { get; set; }
         public string Name { get; set; }
         public string Description { get; set; }
         public double Price { get; set; }
    }
}

How I solved it
I used a combination of @Chris Peacock's and @DavidC's answers.

1. Firstly, rename all entities
To prevent renaming of properties I had to explicitly tell which unique identifiers to rename, because Uniquifier function doesn't tell which type it renames.

public class MyCSharpUtilities : CSharpUtilities
{
    public override string Uniquifier(string proposedIdentifier, ICollection existingIdentifiers)
    {
        var finalIdentifier = base.Uniquifier(proposedIdentifier, existingIdentifiers);

        //Prefix entity names with underscore
        if (finalIdentifier == "Food" ||
            finalIdentifier == "Fruit" ||
            finalIdentifier == "Vegetables")
        {
            finalIdentifier = "_" + finalIdentifier;
        }

        return finalIdentifier;
    }
}

2. Secondly, add the using statement and the [Key]

public class MyEntityTypeGenerator : CSharpEntityTypeGenerator
{
    public MyEntityTypeGenerator(ICSharpHelper cSharpHelper) : base(cSharpHelper) { }   

    public override string WriteCode(IEntityType entityType, string @namespace, bool useDataAnnotations)
    {
        string code = base.WriteCode(entityType, @namespace, useDataAnnotations);           
        string entityTypeName = entityType.Name.Replace("_", "");
        string keyPropertyString = "public int " + entityTypeName + "Id { get; set; }";

        if (code.Contains(keyPropertyString))
        {
            //Add "using" for data annotation
            string oldString = "using System.Collections.Generic;" + Environment.NewLine + Environment.NewLine + "namespace MyNamespace";
            string newString = "using System.Collections.Generic;" + Environment.NewLine + "using System.ComponentModel.DataAnnotations;" + Environment.NewLine + Environment.NewLine + "namespace MyNamespace";
            code = code.Replace(oldString, newString);

            //Add [Key] data annotation
            string newKeyPropertyString = "[Key]" + Environment.NewLine + "\t\t" + keyPropertyString;
            code = code.Replace(keyPropertyString, newKeyPropertyString);
        }

        return code;
    }
}

3. Finally, add these services to Startup.cs

public class CustomEFDesignTimeServices : IDesignTimeServices
{
    //Used for scaffolding database to code
    public void ConfigureDesignTimeServices(IServiceCollection serviceCollection)
    {
        serviceCollection.AddSingleton();
        serviceCollection.AddSingleton();
    }
}