.NET Standard 2.0中的ApplicationDbContext.OnModelCreating（）具有MissingMethodException [英] ApplicationDbContext.OnModelCreating() in .Net Standard 2.0 has MissingMethodException

问题描述

这是我在中发布的问题之一 ；发现不同版本之间存在冲突。或使用aspnetcore.identity 时出现System.MissingMethodException，但我想用一个小例子单独解释一下：

this is one of the problems that I issued in "Found conflicts between different versions" OR System.MissingMethodException when using aspnetcore.identity, but I wanted to explain it separately with a small example:

SetUp：

1. .Net Standard 2.0库


2. .Net Framework 4.7.2 WebForms应用程序

.Net标准库具有以下代码：

The .Net standard Library has this Code:

 public class Class1
    {
        public static void doStuff()
        {
            var optionsBuilder = new DbContextOptionsBuilder<ApplicationDbContext>();
            optionsBuilder.UseSqlServer("MyConnectionString");

            var userStore = new UserStore<ApplicationUser, MyRole, ApplicationDbContext, Guid>(
                new ApplicationDbContext(optionsBuilder.Options)
                ); // the userStore.Users property shows already the exception in the debugger

            AspNetUserManager<ApplicationUser> userManager = new AspNetUserManager<ApplicationUser>(
                userStore,
                null,
                new PasswordHasher<ApplicationUser>(),
                new List<UserValidator<ApplicationUser>>() { new UserValidator<ApplicationUser>() },
                null,
                null,
                null,
                null,
                null
                );

            var x = userManager.Users; // exception throw (see next code snipped)
        }
    }

    public class ApplicationDbContext : IdentityDbContext<ApplicationUser, MyRole, Guid>
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
            : base(options)
        {

        }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder); // after userManager.Users is called the exception is thrown here
        }
    }

在WebForms-Project中只是：

And in the WebForms-Project just:

public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Class1.doStuff();
        }
    }

例外：
System.MissingMethodException：'Methode nicht gefunden： Microsoft.EntityFrameworkCore.Metadata.Builders.IndexBuilder Microsoft.EntityFrameworkCore.Metadata.Builders.EntityTypeBuilder 1.HasIndex（System.Linq.Expressions.Expression 1>）。'

.Net Standard 2.0项目的配置：

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Identity" Version="2.2.0" />
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="2.2.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.1" />
    <PackageReference Include="Microsoft.Extensions.Identity.Stores" Version="3.1.1" />
  </ItemGroup>

</Project>

参考文献：
https://github.com/dotnet/aspnetcore/issues/8467 在这里，他们说要更新为 Microsoft.AspNetCore.Identity 3.x，但我不能这样做，因为它与.Net Standard 2.0项目不兼容，而WebForms项目则需要它。

References: https://github.com/dotnet/aspnetcore/issues/8467 Here they say to update to "Microsoft.AspNetCore.Identity" 3.x, but I cannot do that because its not compatible with the .Net Standard 2.0 project and I need that for the WebForms Project.

所以我的问题将是是否有人知道以其他方式生成Usermanager的解决方法...我需要使用aspnetcore-identity（数据库等已迁移，从而获取和设置用户（并验证）） ）

So my question would be if someone knows a workaround to generate an Usermanager in a different way... I need to Get and Set Users (and validate) using aspnetcore-identity (database etc. is already migrated)

推荐答案

因此，我有一个解决方案：

So, I have a solution for my problem:

使用Microsoft.EntityFrameworkCore.SqlServer 2.2.6版（不 3.1.1，即使它应与.net standard 2.0兼容...）

use Microsoft.EntityFrameworkCore.SqlServer version 2.2.6 (NOT 3.1.1 even though its supposed to work with .net standard 2.0...)

和一系列

• 删除nuget程序包


• 清除nuge t缓存


• 删除本地计算机上的nuget包（在C：/../ Users /.../。nuget文件夹中）


• 将nuget管理格式更改为 PackageReference


• 哭了很多


• 重新安装所有内容并处理了警告，

• deleting nuget packages
• clearing nuget cache
• deleting nuget packages on the local computer (in the C:/../Users/.../.nuget folder)
• changing the nuget management format to "PackageReference"
• cry a lot
• reinstalling everything and dealing with warnings helped

（我不能说问题到底与版本冲突有关）

(I cant say what exactly the issue was regarding the version-conflicts)

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