Nullable reference types

[charlesroddie]

Optional value-type results of stored procedures are correctly given as Nullable by EFCorePowerTools.
It would be good to have this apply to reference types too, e.g. string? in Result classes.
This would make use of this library much more type-safe.

[ErikEJ]

That would require you to support nullable types in your project, and use a new C# version??

[charlesroddie]

Auto-generated code requires an explicit #nullable directive in source

So users shouldn't need to explicitly enable anything in their project files.

[ErikEJ]

But it would still require a new C# version??

[charlesroddie]

Yes C# 8. For netstandard2.1 and netcore3.0 and above, users won't need to do anything.
For netstandard2.0, users will need to add <LangVersion>8.0</LangVersion> to the .csproj.

[ErikEJ]

Ok, so could you give a simple example of the changes required on the generated code?

[charlesroddie]

A procedure UsersInClass returns an Email(nvarchar, null). Currently this class is created:

public partial class UsersInClassResult
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    public byte? Role { get; set; }
}

The change would be to add a ? in Email:

    public string? Email { get; set; }

[ErikEJ]

Thanks, and the #nullable directive??

[charlesroddie]

I missed some = null! which you need to remove a warning.

// <auto-generated> This file has been auto generated by EF Core Power Tools. </auto-generated>
#nullable enable
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;

namespace EFCorePowerTools
{
    public partial class UsersInClassResult
    {
        public int Id { get; set; }
        public string FirstName { get; set; } = null!;
        public string LastName { get; set; } = null!;
        public string? Email { get; set; }
        public byte? Role { get; set; }
    }
}

[ErikEJ]

Hmm what is the code after FirstName, is byte not a value type??

[charlesroddie]

If you have

public string FirstName { get; set; }

then you are saying that FirstName is not null, but there is no non-null value it's being initialized to, and = null! is a way to avoid the warning. You are handling the guarantees of non-nullness manually and some other code will presumably set a non-null value prior to the user seeing it. I think it's the way to deal with traditional C# classes with default values and setters. Anything wrong with my C# @Happypig375 ?

is byte not a value type

Yes the byte? is unchanged.

[ErikEJ]

How would the code generation tool distinguish between FirstName/LastName and Email??? 😕

They are all strings ???

    public string FirstName { get; set; } = null!;
    public string LastName { get; set; } = null!;
    public string? Email { get; set; }

[charlesroddie]

Presumably it gets info on nullability from SQL. It's certainly getting it correctly for value types at present (e.g. in the above, Id(int, non null) is an int, while Role(tinyint, null), is a byte?).

[ErikEJ]

Sorry, I was mixing parameters and result set shape.

So for a non-nullable string (and other reference types) , generate:

public string LastName { get; set; } = default;

and for a nullable string (and other reference types), generate

public string? Email { get; set; }

Is that correctly understood?

dotnet/efcore#15520

[ErikEJ]

OK, interested in doing a PR?

[charlesroddie]

Currently I'm investigating 3 options for improving our database process (EFCorePowerTools / FSharp.Data.Sqlclient / SqlPlus.net). If we decide on EFCorePowerTools I can do a PR but if not I will not be able to.

[ErikEJ]

No worries, I will make the proposed change!

[Happypig375]

@charlesroddie All good.

[ErikEJ]

I plan to implement this as an advanced option initially.

[stgenov]

Please add a row
#nullable enable
directive after the row
because without it VS 2022 (.net Core 6.0) gives a warning:
CS8669: The annotation for nullable reference types should only be used in code within a '#nullable' annotations context. Auto-generated code requires an explicit '#nullable' directive in source.

the warning appears on every row with string?

[ErikEJ]

@stgenov pls create an new issue with details about your csproj.