The type or namespace name 'EntityFrameworkCore' does not exist in the namespace 'Microsoft

Question

I try to do Razor ContosoUniversity (renamed in ContsoObserve initally) for Visual Studio 2017 and get error my .csproj is

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.0</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.0.1" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.1" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Utils" Version="2.0.1" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Update="Microsoft.NETCore.App" Version="2.0.4" />
  </ItemGroup>
  <ItemGroup>
        <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.1" />
    </ItemGroup>
</Project>

I installed all that packages in NuGet

and when I

dotnet aspnet-codegenerator razorpage -m Student -dc SchoolContext -udl -outDir Pages\Students --referenceScriptLibraries

get

Build FAILED. Data\SchoolContext.cs(5,17): error CS0234: The type or namespace name 'EntityFrameworkCore' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\About.cshtml.cs(5,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Contact.cshtml.cs(5,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Error.cshtml.cs(6,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Index.cshtml.cs(6,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Program.cs(7,28): error CS0234: The type or namespace name 'Hosting' does not exist in the namespace 'Microsoft.AspNetCore' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Program.cs(8,28): error CS0234: The type or namespace name 'Configuration' does not exist in the namespace 'Microsoft.Extensions' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Program.cs(9,28): error CS0234: The type or namespace name 'Logging' does not exist in the namespace 'Microsoft.Extensions' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(5,28): error CS0234: The type or namespace name 'Builder' does not exist in the namespace 'Microsoft.AspNetCore' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(6,28): error CS0234: The type or namespace name 'Hosting' does not exist in the namespace 'Microsoft.AspNetCore' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(7,28): error CS0234: The type or namespace name 'Configuration' does not exist in the namespace 'Microsoft.Extensions' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(10,17): error CS0234: The type or namespace name 'EntityFrameworkCore' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\About.cshtml.cs(9,31): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Program.cs(39,23): error CS0246: The type or namespace name 'IWebHost' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(10,34): error CS0246: The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(21,16): error CS0246: The type or namespace name 'IConfiguration' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Contact.cshtml.cs(9,33): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(33,31): error CS0246: The type or namespace name 'IApplicationBuilder' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(33,56): error CS0246: The type or namespace name 'IHostingEnvironment' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(16,16): error CS0246: The type or namespace name 'DbSet<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(16,24): error CS0246: The type or namespace name 'IConfiguration' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Error.cshtml.cs(10,31): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(17,16): error CS0246: The type or namespace name 'DbSet<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(18,16): error CS0246: The type or namespace name 'DbSet<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(20,49): error CS0246: The type or namespace name 'ModelBuilder' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(20,33): error CS0115: 'SchoolContext.OnModelCreating(ModelBuilder)': no suitable method found to override [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Index.cshtml.cs(10,31): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(12,30): error CS0246: The type or namespace name 'DbContextOptions<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] 0 Warning(s) 28 Error(s) I try unload and reload project. Same result.

I add and errors count decrease

Build FAILED.

Data\SchoolContext.cs(5,17): error CS0234: The type or namespace name 'EntityFrameworkCore' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\About.cshtml.cs(5,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Contact.cshtml.cs(5,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Error.cshtml.cs(6,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Index.cshtml.cs(6,32): error CS0234: The type or namespace name 'RazorPages' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Startup.cs(10,17): error CS0234: The type or namespace name 'EntityFrameworkCore' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\About.cshtml.cs(9,31): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(10,34): error CS0246: The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Contact.cshtml.cs(9,33): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Error.cshtml.cs(10,31): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(16,16): error CS0246: The type or namespace name 'DbSet<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Pages\Index.cshtml.cs(10,31): error CS0246: The type or namespace name 'PageModel' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(17,16): error CS0246: The type or namespace name 'DbSet<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(18,16): error CS0246: The type or namespace name 'DbSet<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(20,49): error CS0246: The type or namespace name 'ModelBuilder' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(20,33): error CS0115: 'SchoolContext.OnModelCreating(ModelBuilder)': no suitable method found to override [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] Data\SchoolContext.cs(12,30): error CS0246: The type or namespace name 'DbContextOptions<>' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\ContosoObserve.csproj] 0 Warning(s)

Solution 1

Change your package reference to Microsoft.AspNetCore.All (currently verrsion 2.0.3). That will include Entity Framework (plus more than you will need).

Also, don't use Update on the PackageReference element, use Include.

Solution 2

I was getting the same error message even though I have already installed "Microsoft.EntityFrameworkCore" on Visual Studio 2019. I did uninstall & reinstall and it worked fine.

Comments

[Neil]

Have you done dotnet restore to get all the nuget packages?

[streamc]

yes. of cource. I add <PackageReference Include="Microsoft.AspNetCore" Version="2.0.1" /> and errors count turn from 28 to 17

[streamc]

The specified framework 'Microsoft.NETCore.App', version '2.0.4' was not found. - Check application dependencies and target a framework version installed at: \ - Alternatively, install the framework version '2.0.4'.

[Daniel A. White]

@ifooi i dont know what you changed?

[streamc]

Yes, I add Microsoft.AspNetCore.All but Microsoft.NETCore.App" Version="2.0.4 remains. Do I need to uninstall it?

[Daniel A. White]

just have the single PackageReference.

[streamc]

Severity Code Description Project File Line Suppression State Error NU1605 Detected package downgrade: Microsoft.NETCore.App from 2.0.3 to 2.0.0. Reference the package directly from the project to select a different version. ContosoObserve -> Microsoft.VisualStudio.Web.CodeGeneration.Tools 2.0.1 -> Microsoft.NETCore.App (>= 2.0.3) ContosoObserve -> Microsoft.NETCore.App (>= 2.0.0) ContosoObserve C:\Users\STR\source\repos\ContosoObser‌​ve\ContosoObserve\Co‌​ntosoObserve.csproj ‌​1

[streamc]

I reinstall all projects and I have No executable found matching command "dotnet-aspnet-codegenerator"

[Daniel A. White]

@ifooi try dotnet restore

[streamc]

I always do It!

[streamc]

Restore completed in 83,71 ms for C:\Users\STR\source\repos\ContosoObserve\ContosoObserve\Cont‌​osoObserve.csproj.

[streamc]

No executable found matching command "dotnet-aspnet-codegenerator"

[streamc]

O, nice all works! a removed <ItemGroup> <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.0" /> </ItemGroup> and now I add it again

[streamc]

My .csprojis <Project Sdk="Microsoft.NET.Sdk.Web"> <PropertyGroup> <TargetFramework>netcoreapp2.0</TargetFramework> </PropertyGroup> <ItemGroup> <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.3" /> <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.0.1" /> <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Utils" Version="2.0.1" /> </ItemGroup> <ItemGroup> <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.0" /> </ItemGroup>

[streamc]

Thank You for your help!