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Documentation for Entity Framework Core and Entity Framework 6
https://docs.microsoft.com/ef/
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Template Processing Failed:(4,47): error CS0234: #796

Closed xsqian closed 6 years ago

xsqian commented 6 years ago

There was an error running the selected code generator: ‘There was an error running the template C:\User\xsqian.nuget\packages\microsoft.visualstudio.web.codegenerators.mvc\2.1.1\Templates\ControlerGenerator\MvcControllerWithContext.cshtml: Template Processing Failed:(4,47): error CS0234: The type of namespace name ‘Hosting’ does not exist in the namespace ‘Microsoft.AspNetCore.Razor’ (are you missing an assembly reference?) (20,41): error CS0234: The type or namespace name ‘Hosting’ does not exist in the namespace ‘Microsoft.AspNetCore.Razor’ (are you missing an assembly reference?)’

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ajcvickers commented 6 years ago

@Rick-Anderson Any ideas on this?

Rick-Anderson commented 6 years ago

@xsqian Where exactly in the tutorial did you get that error?

we've had this reported several times but I haven't been able to reproduce the problem.

What has helped in the past:

@seancpeters we've seen this error a few times.

@xsqian can you try the following:

dotnet new webapp -o ContosoUniversity
cd ContosoUniversity
dotnet run

Add Student class

using System;
using System.Collections.Generic;

namespace ContosoUniversity.Models
{
    public class Student
    {
        public int ID { get; set; }
        public string LastName { get; set; }
        public string FirstMidName { get; set; }
        public DateTime EnrollmentDate { get; set; }
    }
}

Scaffold the student model

dotnet add package Microsoft.VisualStudio.Web.CodeGeneration.Design --version 2.1.0
dotnet aspnet-codegenerator razorpage -m Student -dc ContosoUniversity.Models.SchoolContext -udl -outDir Pages\Students --referenceScriptLibraries
dotnet ef migrations add Initial
dotnet ef database update

Test the app. Navigate to /Students

yamazaroon commented 6 years ago

I receive this same exact error when performing the "Create a Controller" step: https://docs.microsoft.com/en-us/ef/core/get-started/aspnetcore/existing-db#create-a-controller

After performing these steps: Right-clicking on the controller folder Selecting the MVC Controller with views, using Entity Framework option Selecting the model class and Data context class After clicking the "Add" button, the above-mentioned error is produced.

Rick-Anderson commented 6 years ago

@yamazaroon can you try the steps I've outlined above - starting with dotnet new webapp -o ContosoUniversity

zackshine commented 6 years ago

I met this problem today,and I changed the version of Microsoft.AspNetCore.All in .csproj file then it worked in asp.net core2.1.

  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.1.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.1.1" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.1.1" />
  </ItemGroup>

  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.4" />
  </ItemGroup>
Rick-Anderson commented 6 years ago

@zackshine using M.A.All is discouraged. See https://docs.microsoft.com/en-us/aspnet/core/fundamentals/metapackage?view=aspnetcore-2.1

dbiehle commented 6 years ago

I encountered the same error at the Create a Controller step (see @yamazaroon 's comment above) and tried the steps @Rick-Anderson suggested:

None of these solved the issue, so I deleted the project and re-ran this tutorial using ASP.NET Core Templates 2.1 instead of ASP.NET Core Templates 2.0 as directed in the Create a new project section. With this change I was able to complete the tutorial successfully and add new URLs to the Blog table.

joelbenford commented 6 years ago

I encountered the same problem as @xsqian reported. I resolved it as suggested by @dbiehle: .Net Core version, repair VS2017, start the project as .Net Core 2.1.

I was unable to install the Nuget packages per the tutorial, it seems I had 2.1.1 and .NC wanted 2.1.0. So I manually adjusted my.csproj thus:

netcoreapp2.1

I was then able to get past the previous error.

One thing I note: in the tutorial, immediately after clicking "Add Controller", it says... Select Full Dependencies and click Add You can ignore the instructions in the ScaffoldingReadMe.txt file that opens

I don't now what that's about, I got no option to do that, I went straight from clicking "add controller" to "Select MVC Controller with views, using Entity Framework and click Ok". There was nowhere to select "full dependencies" in between. Not sure if this helps...

joelbenford commented 6 years ago

The comment system my csproj as html. Here it is with the angle brackets converted to curly braces... {Project Sdk="Microsoft.NET.Sdk.Web"}

{PropertyGroup} {TargetFramework}netcoreapp2.1{/TargetFramework} {/PropertyGroup}

{ItemGroup} {PackageReference Include="Microsoft.AspNetCore.App" /} {PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.0" /} {PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.1.0" /} {PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.1.0" /} {/ItemGroup}

{/Project}

Rick-Anderson commented 6 years ago

@joelbenford add version to M.A.App

{PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.0" /}

but 2.1.1

Rick-Anderson commented 6 years ago

Closing. You get this error when you don't have the current .NET Core SDK installed.