When Using a Custom Type as a Primary Key,The Overloaded == Operator for This Custom Type,Should Perhaps Provide More Robust Coding Guidance Related to Nullable Reference Types

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Title

When Using a Custom Type as a Primary Key
The Overloaded == Operator for This Custom Type
Should Perhaps
Provide More Robust Coding Guidance Related to Nullable Reference Types

Phenomenon

When Running the Following Code
Near the Overloaded == Operator Method
An Error is Triggered:
System.NullReferenceException: "Object reference not set to an instance of an object."

Analysis and Opinion

This Situation
Is Equivalent to Ef Core Requiring That
The left and right Parameters of the Overloaded == Operator Method
Must Use Nullable Reference Types
And Not Non-nullable Reference Types

Ef Core Might Be Responsible for Detecting When
The Overloaded == Operator Method
Uses Non-nullable Reference Types as Parameters
Which Can Potentially Lead to Errors

Or
There Should Be Some Out-of-the-box (Present by Default) Solution
To Warn About the Existence of Such Code That Could Cause Errors

标题

当把自定义类型作为主键时
对于该自定义类型的==运算符重载方法
或许应该
提供，与可空引用类型，相关的
更完善的编码提示

现象

当运行下面的代码的
在==运算符重载方法的附近
会触发报错
System.NullReferenceException:“Object reference not set to an instance of an object.”

分析和意见

这种情况
相当于，Ef Core要求
==运算符重载方法，的left和right参数
必须使用，可空的，引用类型
不允许使用，不可空的，引用类型

Ef Core 可能有责任，识别到
==运算符重载方法
使用了，不可空的，引用类型，作为参数
进而，有一定概率将引发报错

或者
应该，提供某种开箱即用（默认情况下就有）的方案
来提示，这种可能引发报错的代码，的存在

Code

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Storage.ValueConversion;

namespace AConsoleApp;

internal class Program
{
    class MyDbContext : DbContext
    {
        public DbSet<Student> Students { get; private set; }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer
                ("Server=localhost\\SqlServerA;Database=MyDbContext;User=sa;Password=abcd;TrustServerCertificate=True;");
        }
        protected override void ConfigureConventions
            (ModelConfigurationBuilder modelConfigurationBuilder)
        {
            modelConfigurationBuilder.Properties<StudentId>().HaveConversion<StudentIdConverter>();
        }
    }
    static void Main(string[] args)
    {
        {
            using var db = new MyDbContext();
            db.Database.EnsureDeleted();
            db.Database.EnsureCreated();
        }
        {
            using var db = new MyDbContext();
            var studentA = new Student("Tom");
            db.Students.Add(studentA);
            db.SaveChanges();
        }
    }
    [PrimaryKey(nameof(Id))]
    class Student
    {
        public StudentId Id { get; private set; }
        public string Name { get; set; }
        public Student(string name)
        {
            this.Id = new();
            this.Name = name;
        }
    }
    public class StudentIdConverter : ValueConverter<StudentId, long>
    {
        public StudentIdConverter()
            : base(
                v => v.Ticks,
                v => new StudentId(v))
        {
        }
    }
    public partial class StudentId
    {
        public long Ticks { get; private set; }
        public StudentId()
        {
            this.Ticks = DateTime.Now.Ticks;
        }
        public StudentId(long ticks)
        {
            this.Ticks = ticks;
        }
        // System.NullReferenceException:“Object reference not set to an instance of an object.”
        public static bool operator ==(StudentId left, StudentId right)
            => left.Ticks == right.Ticks;
        public static bool operator !=(StudentId left, StudentId right)
            => left.Ticks != right.Ticks;
    }

}