内存数据库中的实体框架 7 异常

本文关键字：框架 异常 实体 数据库 内存 | 更新日期: 2023-09-27 18:31:14

使用内存数据库进行 EF 7 的单元测试时遇到了问题。以下应用程序将演示该问题。

using System;
using Microsoft.Data.Entity;
using Microsoft.Data.Entity.Infrastructure;
namespace EF7InMemoryBug
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Program p = new Program();
            MembershipContext m1 = p.GetNewContext();
            MembershipContext m2 = p.GetNewContext();
            foreach (var member in m1.Members)
            {
                Console.WriteLine(member);
            }
        }
        private MembershipContext GetNewContext()
        {
            var optionsBuilder =
                new DbContextOptionsBuilder<MembershipContext>();
            optionsBuilder.UseInMemoryDatabase();
            MembershipContext context = new MembershipContext(optionsBuilder.Options);
            Member member1 = new Member()
            {
                MemberId = 1,
                FirstName = "James",
                LastName = "Jones"
            };
            context.Members.Add(member1);
            context.SaveChanges();
            return context;
        }
    }
    public class Member
    {
        public int MemberId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public override string ToString()
        {
            return $"{MemberId} {FirstName} {LastName}";
        }
    }
    public class MembershipContext : DbContext
    {
        public MembershipContext(DbContextOptions options)
        : base(options) {}
        public DbSet<Member> Members { get; set; }
    }
}

调用MembershipContext m2 = p.GetNewContext();后，context.SaveChanges() 上会引发异常。

EntityFramework.Core 中发生类型为"System.ArgumentException"的异常.dll但未在用户代码中处理

其他信息：具有相同键但不同的元素 值已存在。钥匙： Microsoft.Data.Entity.ChangeTracking.Internal.SimpleKeyValue'1[System.Int32]

我知道发生了什么，但我不知道为什么。

当第二次调用MembershipContext context = new MembershipContext(optionsBuilder.Options);时，将创建上下文，但是context.Members已经具有我第一次创建上下文时的条目，因此异常。

内存数据库中的实体框架 7 异常

这不是一个错误，而是一个功能。https://github.com/aspnet/EntityFramework.Docs/issues/95

以下是使用 DI 的建议方法。

using System;
using Microsoft.Data.Entity;
using Microsoft.Data.Entity.Infrastructure;
using Microsoft.Extensions.DependencyInjection;
namespace EF7InMemoryBug
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Program p = new Program();
            MembershipContext m1 = p.GetNewContext();
            MembershipContext m2 = p.GetNewContext();
            foreach (var member in m1.Members)
            {
                Console.WriteLine(member);
            }
            foreach (var member in m2.Members)
            {
                Console.WriteLine(member);
            }
        }
        private MembershipContext GetNewContext()
        {
            var serviceCollection = new ServiceCollection();
            serviceCollection
                .AddEntityFramework()
                .AddInMemoryDatabase()
                .AddDbContext<MembershipContext>(c => c.UseInMemoryDatabase());
            MembershipContext context = serviceCollection.BuildServiceProvider().GetService<MembershipContext>();
            Member member1 = new Member()
            {
                MemberId = 1,
                FirstName = "James",
                LastName = "Jones"
            };
            context.Members.Add(member1);
            context.SaveChanges();
            return context;
        }
    }
    public class Member
    {
        public int MemberId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public override string ToString()
        {
            return $"{MemberId} {FirstName} {LastName}";
        }
    }
    public class MembershipContext : DbContext
    {
        public MembershipContext(DbContextOptions options)
        : base(options) {}
        public DbSet<Member> Members { get; set; }
    }
}
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