ASP.NET Core WebApp（.NET Core）缺少DataAnnotations

Following situation:
我有一个包含多个项目的.sln（数据访问，业务对象，业务逻辑，Web服务器） .
Web-Project是一个ASP.NET核心Web应用程序，使用.Net-Core 1.1，具有单独的用户帐户授权（Identity）和"WebApplication" -Template .
其余项目使用.Net-Framework 4.6.2 .

现在我要从Web服务器中删除DBContext，而不是像data-access-project中那样使用它 .
我相应地设置了我的ApplicationDBContext，我的用户实体扩展了IdentityUser . 我还更改了web-server-project中的所有内容以使用ApplicationDBContext（在我的例子中称为WTHListModell） .
我还有项目WTHList.GO（业务对象）和WTHList.DZ（数据访问）的引用 .

Now here comes the problem:
使用完整的.NET-Framework for Web-Server（创建".NET-Core Web-Application (.Net-Framework)"）这样做是成功的，并且工作得很好 .
使用.Net-Core 1.1每当我尝试登录或注册用户时，我都会收到关于"System.ComponentModel.DataAnnotations"的FileNotFound-Exception .
现在我已经读过，DataAnnotations与.Net-Core不兼容，我也试图将其他NuGet-Packages和Assemblies添加到Web-Project中 .

我不知道我还能做些什么，因为我应该将.NET-Core Framework 1.1用于Web-Projekt并且它不断给我这个特殊的错误 .

Has anybody got a clue on how to solve this issue?
我已经搜索了一段时间，但我还没有找到解决方案......

如果它有任何相关性：我正在使用VS2017企业级RC .

提前致谢 .

UPDATE 这是csproj文件的内容：

<Project ToolsVersion="15.0" Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup Label="Globals">
    <SccProjectName>SAK</SccProjectName>
    <SccProvider>SAK</SccProvider>
    <SccAuxPath>SAK</SccAuxPath>
    <SccLocalPath>SAK</SccLocalPath>
  </PropertyGroup>
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp1.1</TargetFramework>
    <PreserveCompilationContext>true</PreserveCompilationContext>
  </PropertyGroup>
  <PropertyGroup>
    <PackageTargetFallback>$(PackageTargetFallback);portable-net45+win8+wp8+wpa81;</PackageTargetFallback>
  </PropertyGroup>
  <PropertyGroup>
    <UserSecretsId>aspnet-WTHList.Web2-ab5b6dbd-698d-4877-a2b3-6dd9b7a37960</UserSecretsId>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="1.1.0" />
    <PackageReference Include="Microsoft.NETCore.App" Version="1.0.1" />
    <PackageReference Include="Microsoft.AspNetCore.Diagnostics" Version="1.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="1.0.1" />
    <PackageReference Include="Microsoft.AspNetCore.Routing" Version="1.0.1" />
    <PackageReference Include="Microsoft.AspNetCore.Server.IISIntegration" Version="1.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel" Version="1.0.1" />
    <PackageReference Include="Microsoft.AspNetCore.StaticFiles" Version="1.0.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="1.0.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="1.0.0" />
    <PackageReference Include="Microsoft.Extensions.Logging" Version="1.1.0" />
    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="1.0.0" />
    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="1.0.0" />
    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="1.0.0" />
    <PackageReference Include="Microsoft.VisualStudio.Web.BrowserLink.Loader" Version="14.0.0" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Authentication.Cookies" Version="1.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore" Version="1.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="1.0.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="1.1.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="1.1.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer.Design" Version="1.0.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="1.1.0-preview4-final" />
    <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="1.0.0" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="1.0.0-msbuild2-final" />
  </ItemGroup>
  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="1.0.0-msbuild2-final" />
    <DotNetCliToolReference Include="Microsoft.Extensions.SecretManager.Tools" Version="1.0.0-msbuild2-final" />
    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="1.0.0-msbuild2-final" />
  </ItemGroup>
  <ItemGroup>
    <ProjectReference Include="..\WTHList.DZ\WTHList.DZ.csproj" />
    <ProjectReference Include="..\WTHList.GL\WTHList.GL.csproj" />
    <ProjectReference Include="..\WTHList.GO\WTHList.GO.csproj" />
  </ItemGroup>
</Project>