我似乎无法解决 Entity Framework 6 的常见问题。我已经在 SO 上查看了与此问题相关的许多主题，并且无法找到适合我的特定情况的解决方案。
到目前为止，我一直在使用 localdb 和代码优先迁移进行开发，效果很好。但现在我将其移动到实际的 SQL Server 实例，它在尝试迁移时抛出以下错误：
“具有固定名称“System.Data.SqlClient;”的 ADO.NET 提供程序未在计算机或应用程序配置文件中注册，或者无法加载。有关详细信息，请参阅内部异常。 在System.Data.Common.DbProviderFactories.GetFactory（字符串providerInvariantName）“
我尝试了以下修复：
1）卸载并重新安装实体框架
2）添加了code并使用：
public abstract class BaseDomainContext : DbContext
{
static BaseDomainContext()
{
// ROLA - This is a hack to ensure that Entity Framework SQL Provider is copied across to the output folder.
// As it is installed in the GAC, Copy Local does not work. It is required for probing.
// Fixed "Provider not loaded" error
var ensureDLLIsCopied = System.Data.Entity.SqlServer.SqlProviderServices.Instance;
}
}
作为我的 DbSet 类的基类。
3）将所有内容添加到新的解决方案中并收到相同的错误。
4）删除写入上下文并尝试仅读取迁移，仍然失败。
5）尝试使用来自的信息进行多次重写MSDN
6）我已确认EntityFramework.SqlServer.dll位于我的bin目录中。它也被正确引用。另外，我的解决方案下只有一个项目。
7）确认我没有在视图下使用WebConfig。
8) 确认 bin 文件夹中有 System.Data dll。
在上述每个步骤之后完成清理/重建和删除现有迁移文件夹。
我无法解释为什么我仍然收到此错误。
网页配置
<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="webpages:Version" value="3.0.0.0" />
<add key="webpages:Enabled" value="false" />
<add key="ClientValidationEnabled" value="true" />
<add key="UnobtrusiveJavaScriptEnabled" value="true" />
</appSettings>
<connectionStrings>
<add name="ReadContext" connectionString="Server=Sql2014intsnace;Database=database;User Id=secret; Password=secret;" providerName="System.Data.SqlClient;" />
<add name="WriteContext" connectionString="Server=Sql2014intsnace;Database=database;User Id=secret; Password=secret;" providerName="System.Data.SqlClient;" />
</connectionStrings>
<system.web>
<compilation debug="true" targetFramework="4.5" />
<httpRuntime targetFramework="4.5" />
<authentication mode="Windows" />
<authorization>
<deny users="?" />
</authorization>
</system.web>
<system.webServer>
<handlers>
<remove name="ExtensionlessUrlHandler-Integrated-4.0" />
<remove name="OPTIONSVerbHandler" />
<remove name="TRACEVerbHandler" />
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
</handlers>
</system.webServer>
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="Microsoft.Owin" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Microsoft.Owin.Security.OAuth" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Microsoft.Owin.Security.Cookies" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Microsoft.Owin.Security" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Newtonsoft.Json" culture="neutral" publicKeyToken="30ad4fe6b2a6aeed" />
<bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-5.2.2.0" newVersion="5.2.2.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Optimization" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="1.1.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-1.5.2.14234" newVersion="1.5.2.14234" />
</dependentAssembly>
</assemblyBinding>
</runtime>
<entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
<providers>
<provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
</providers>
<contexts>
<context type="ProjectName.Models.ReadContext, ProjectName">
<databaseInitializer type="System.Data.Entity.MigrateDatabaseToLatestVersion`2[[ProjectName.Models.ReadContext, ProjectName], [ProjectName.Migrations.Configuration, ProjectName]], EntityFramework" />
</context>
</contexts>
</entityFramework>
</configuration>
你有这个：
<add name="ReadContext"
connectionString="Server=Sql2014intsnace;Database=database;User Id=secret; Password=secret;"
providerName="System.Data.SqlClient;" /> <-- semi-colon
应该是这样的：
<add name="ReadContext"
connectionString="Server=Sql2014intsnace;Database=database;User Id=secret; Password=secret;"
providerName="System.Data.SqlClient" /> <-- no semi-colon
否则，您将告诉 ADO 查找名为System.Data.SqlClient;- 没有一个。