Why can't I install Microsoft.Owin.Host.SystemWeb package for EF Core 1.1?

I'm trying to upload an image in a folder through an MVC web application and I need the HttPostedFileBase attribute therefore I need the System.Web package. I try to install it from NuGet package manager but every single version seems to be not compatible. How can I download and install the System Web package?

This is the package link: https://www.nuget.org/packages/Microsoft.Owin.Host.SystemWeb/3.1.0/

This is the CSPROJ file:

<PackageReferenceInclude="Microsoft.ApplicationInsights.AspNetCore"Version="2.0.0"/><PackageReferenceInclude="Microsoft.AspNetCore"Version="1.1.4"/><PackageReferenceInclude="Microsoft.AspNetCore.Mvc"Version="1.1.4"/><PackageReferenceInclude="Microsoft.AspNetCore.StaticFiles"Version="1.1.3"/><PackageReferenceInclude="Microsoft.EntityFrameworkCore.Design"Version="1.1.5"/><PackageReferenceInclude="Microsoft.EntityFrameworkCore.SqlServer"Version="1.1.5"/><PackageReferenceInclude="Microsoft.EntityFrameworkCore.SqlServer.Design"Version="1.1.2"/><PackageReferenceInclude="Microsoft.EntityFrameworkCore.Tools"Version="1.1.5"/><PackageReferenceInclude="Microsoft.Extensions.Logging.Debug"Version="1.1.2"/><PackageReferenceInclude="Microsoft.VisualStudio.Web.BrowserLink"Version="1.1.3"/><PackageReferenceInclude="Microsoft.VisualStudio.Web.CodeGeneration.Design"Version="1.1.1"/><PackageReferenceInclude="PagedList.Core.Mvc"Version="1.0.1"/>