为什么我在运行更新数据库时得到 Object 引用未设置为 object 的实例

Question

First time working with entity framework, I've been testing with an in memory database which has been working fine but wanted to start working on a persistent database using sqlite.

I've got the model and context created, when I run Add-Migration in the Package Manager Console it seems to work fine but when I then run the Update-Database function I always get a 'Object reference not set to an instance of an object' error but I can't work out why, any help really appreciated, been searching around for a while and can't see anything.

Screenshot of the reported error

I've got four model classes and the context class so not sure I can include all the code snippets here but happy to if folk think it's needed to get anywhere.

Thanks.

Answer 1

OK so I found out what the issue was. The "Object reference not set to an instance of an object" in this case was due to the fact that I didn't have a reference to Microsoft.EntityFrameworkCore.Sqlite. I did have a reference to Microsoft.EntityFrameworkCore.Sqlite.Core which is what allowed the project to build OK but apparently this is required for the Update-Database call.

Also for anyone else needing to take a step back and just confirm they aren't going crazy, this is a good website describing what is needed. I used this just to confirm everything worked OK and I hadn't missed something (which I obviously had).

TL:DR - Make sure you have a reference to Microsoft.EntityFrameworkCore.Sqlite