无法使用实体框架找到或加载 Npgsql

Posted 2023-02-16

【中文标题】无法使用实体框架找到或加载 Npgsql

【英文标题】：Unable to find or load Npgsql with Entity Framework

【发布时间】：2016-05-27 07:12:58

【问题描述】：

我完全迷路了。在 Visual Studio 2015 中，我创建了一个 WCF 库服务项目并定义了服务和服务接口。

EntityFramework、EntityFramework.SqlServer、EntityFramework6.Npgsql 和 Npgsql 与 NuGet 控制台一起安装：

PM> 安装包 EntityFramework6.Npgsql -Version 3.0.5

将库服务设置为启动然后正确启动调试（f5） 阅读可用的程序。然而，在测试任何程序在 WcfSvcHost，我收到以下错误：

具有不变名称“Npgsql”的 ADO.NET 提供程序不是 在机器或应用程序配置文件中注册，或无法注册 加载。有关详细信息，请参阅内部异常。

我做错了什么？

这里是 App.config 文件：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
  </configSections>
  <appSettings>
    <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" />
  </appSettings>
  <system.web>
    <compilation debug="true" />
  </system.web>
  <!-- When deploying the service library project, the content of the config file must be added to the host's 
  app.config file. System.Configuration does not support config files for libraries. -->
  <system.serviceModel>
    <services>
      <service name="NovaMedicalService.MedicalService">
        <endpoint address="" binding="basicHttpBinding" contract="NovaMedicalService.IMedicalService">
          <identity>
            <dns value="localhost" />
          </identity>
        </endpoint>
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8733/Design_Time_Addresses/NovaMedicalService/MedicalService/" />
          </baseAddresses>
        </host>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <!-- To avoid disclosing metadata information, 
          set the values below to false before deployment -->
          <serviceMetadata httpGetEnabled="True" httpsGetEnabled="True" />
          <!-- To receive exception details in faults for debugging purposes, 
          set the value below to true.  Set to false before deployment 
          to avoid disclosing exception information -->
          <serviceDebug includeExceptionDetailInFaults="False" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v12.0" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
      <provider invariantName="Npgsql" type="Npgsql.NpgsqlServices, EntityFramework6.Npgsql" />
    </providers>
  </entityFramework>
  <connectionStrings>
    <add name="chaosEntities" connectionString="metadata=res://*/ChaosModel.csdl|res://*/ChaosModel.ssdl|res://*/ChaosModel.msl;provider=Npgsql;provider connection string=&quot;Database=chaos;Host=localhost;Password=yuyuyu;Username=ooosos&quot;" providerName="System.Data.EntityClient" />
  </connectionStrings>
</configuration>

有人可以帮忙吗？我完全迷路了。

TIA

【参考方案1】：

问题解决了。我忽略了补充：

<system.data>
    <DbProviderFactories>
      <remove invariant="Npgsql" />
      <add name="Npgsql Data Provider" invariant="Npgsql" description=".Net Data Provider for PostgreSQL" type="Npgsql.NpgsqlFactory, Npgsql, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" support="FF" />
    </DbProviderFactories>
  </system.data>

（见Visual Studio Support (DDEX)

【讨论】：

那么这个解决方案的解释是什么？

【参考方案2】：

卸载并重新安装 Npgsql.vsix 解决了这个问题。