asp.net core 和 postgresql 迁移中的调用目标已抛出异常

问题描述

我正在尝试创建一个项目。这就是我从 this link 下载启动模板的原因。然后我尝试用asp.net core进行配置。我将连接字符串设置为 "Default": "User ID=postgres;Password=**********;Host=localhost;Port=5432;Database=LibraryManagementDb;Pooling=true;"。然后在 LibraryManagementDbContextConfigurer 类中将 UsesqlServer 更改为 UseNpgsql。

`

public static void 
     Configure(DbContextOptionsBuilder<LibraryManagementDbContext> 
      builder,string connectionString)
        {
          builder.UseNpgsql(connectionString);
     }

    public static void 
     Configure(DbContextOptionsBuilder<LibraryManagementDbContext> 
       builder,DbConnection connection)
    {
        builder.UseNpgsql(connection);
    }

`

并将以下代码添加到 DbContext 类

`

 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<ApplicationLanguageText>()
            .Property(p => p.Value)
            .HasMaxLength(100); // any integer that is smaller than 10485760
    }

`

并从 Migration 文件夹中删除所有迁移类并在包管理器控制台中运行 add-migration Initial_Migration 命令

但是我得到了异常已被调用的目标抛出。错误

这是整个例外

`

PM> add-migration Initial_Migration
Build started...
Build succeeded.
System.Reflection.TargetInvocationException: Exception has been 
thrown by the target of an invocation.
---> System.TypeLoadException: Method 'get_Info' in type  
'Microsoft.EntityFrameworkCore.Infrastructure.
Internal.NpgsqlOptionsExt 
  ension' from assembly 'Npgsql.EntityFrameworkCore.Postgresql,Version=2.1.0.0,Culture=neutral,PublicKeyToken=5d8b90d52f46fda7' 
does not have an implementation.
at Microsoft.EntityFrameworkCore
.NpgsqlDbContextOptionsExtensions.UseNpgsql[TContext]
   at LibraryManagement.EntityFrameworkCore
.LibraryManagementDbContextConfigurer
.Configure(DbContextOptionsBuilder`1 builder,String 
connectionString) in D:\6.0.0\aspnet- 
core\src\LibraryManagement.EntityFrameworkCore
\EntityFrameworkCore\LibraryManagementDbContextConfigurer.cs:line 
 10
 at LibraryManagement.EntityFrameworkCore
.LibraryManagementDbContextFactory.CreateDbContext(String[] args) 
in D:\6.0.0\aspnet-core\src\LibraryManagement.EntityFrameworkCore
\EntityFrameworkCore\LibraryManagementDbContextFactory.cs:line 17
--- End of inner exception stack trace ---
at System.RuntimeMethodHandle.InvokeMethod(Object target,Object[] 
arguments,Signature sig,Boolean constructor,Boolean 
wrapExceptions)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj,BindingFlags invokeAttr,Binder binder,Object[] parameters,CultureInfo culture)
at System.Reflection.MethodBase.Invoke(Object obj,Object[] 
parameters)
at Microsoft.EntityFrameworkCore.Design
.Internal.DbContextOperations.CreateContextFromFactory(Type 
factory,Type contextType)
at 
Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations. 
<>c__displayClass16_0.<FindContextFactory>b__1()
at Microsoft.EntityFrameworkCore.Design.Internal
.DbContextOperations.CreateContext(Func`1 factory)
at Microsoft.EntityFrameworkCore.Design.Internal
.DbContextOperations.CreateContext(String contextType)
at Microsoft.EntityFrameworkCore.Design.Internal
.MigrationsOperations.AddMigration(String name,String outputDir,String contextType,String namespace)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor
.AddMigrationImpl(String name,String 
contextType,String namespace)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor
.AddMigration.<>c__displayClass0_0.<.ctor>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor
.OperationBase.<>c__displayClass3_0`1.<Execute>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor
.OperationBase.Execute(Action action)
Exception has been thrown by the target of an invocation.

`

我该如何解决这个问题？？？请帮忙...

解决方法

通过更新'Npgsql.EntityFrameworkCore.PostgreSQL'解决了这个问题