adding a foreign key with Code First migration

Question

I have an error when trying to update my database after adding a migration.

Here are my classes before add-migration

public class Product
{
    publi         


        

Answer 1

This is an old issue but currently there is no need to create a separate migration and this issue can be solved using a few steps:

1. Run Add-Migration with the entity changes (a new non-nullable reference property added, ProductId in this case) to scaffold a new migration class
2. Modify newly added migration to create a nullable column (nullable: true) instead of non-nullable
3. Below AddColumn add Sql command setting the value of the column as needed
4. Below add AlterColumn command which will make the column non-nullable as intended

In the example above this would look like:

    public override void Up()
    {
        AddColumn("dbo.ProductFeatures", "ProductId", c => c.Int(nullable: true));
        Sql("UPDATE [dbo].[ProductFeatures] SET ProductId = (SELECT TOP 1 [Id] FROM [dbo].[Products])");
        AlterColumn("dbo.ProductFeatures", "ProductId", c => c.Int(nullable: false));
        CreateIndex("dbo.ProductFeatures", "ProductId");
        AddForeignKey("dbo.ProductFeatures", "ProductId", "dbo.Products", "Id");
    }