dotnet build error - the project 'Web' must provide a value for Configuration

Steps to reproduce

I run this command to build an aspnet core project(Web is the startup project)

dotnet build X.sln -c Release --no-cache --source “\\local_source\packages” --source “https://api.nuget.org/v3/index.json”

Expected behavior

Build should be successful.

The same issue was raised by our TFS autobuild. When I tried on my local machine I get the same error. But I have no clue what could be wrong here. There is this post here but I doubt this is related to razor only. And also, the solution there was not very clear and (re-installing the sdk) won’t be an option (especially on the build server).

Actual behavior

I get the following error right after the packages has been restored:

C:\Users\MyUser\.nuget\packages\microsoft.aspnetcore.razor.design\2.1.1\build\netstandard2.0\Microsoft.AspNetCore.Razor.Design.CodeGeneration.targets(121,5): error : The project D:\Workspaces\X\src\Web must provide a value for Configuration. [D:\Workspaces\X\src\Web\Web.csproj]

Environment data

dotnet --info output:

.NET Core SDK (reflecting any global.json): Version: 2.1.403 Commit: 04e15494b6

Runtime Environment: OS Name: Windows OS Version: 6.1.7601 OS Platform: Windows RID: win7-x64 Base Path: C:\Program Files\dotnet\sdk\2.1.403\

Host (useful for support): Version: 2.1.5 Commit: 290303f510

.NET Core SDKs installed: 1.0.4 [C:\Program Files\dotnet\sdk] 2.1.4 [C:\Program Files\dotnet\sdk] 2.1.102 [C:\Program Files\dotnet\sdk] 2.1.103 [C:\Program Files\dotnet\sdk] 2.1.104 [C:\Program Files\dotnet\sdk] 2.1.200 [C:\Program Files\dotnet\sdk] 2.1.201 [C:\Program Files\dotnet\sdk] 2.1.202 [C:\Program Files\dotnet\sdk] 2.1.300 [C:\Program Files\dotnet\sdk] 2.1.400 [C:\Program Files\dotnet\sdk] 2.1.402 [C:\Program Files\dotnet\sdk] 2.1.403 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed: Microsoft.AspNetCore.All 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 1.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 1.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs: https://aka.ms/dotnet-download

[tomRedox]

I had this infuriating issue when migrating a .NET Core 2.2 app to core 3.0. The issue turned out to be that I was still referencing Microsoft.AspNetCore.Razor.Design Version=“2.2.0” in the .proj file’s package references. Deleting that reference (which isn’t needed at all as Razor.Design is now part of AspNetCore library) fixed the issue.

Once I’d done that, I then got hundreds of errors about nullable objects being a new feature not compatible with razor. That was because I had <LangVersion>Latest</LangVersion> in my .proj file. Removing that line fixed that issue and got the project running again.

You might need to restart VS too in some cases (see @JerryBian’s comment below).

(I’ve stuck this answer on Stack Overflow too to make it a bit more visible as it looks like a lot of people are having this issue. So if none of the above fixes the issue you could check that question too in case more answers get added there)

[JerryBian]

Exactly like @tomRedox explained.

For me just one additional step - restart Visual Studio to make it effective. Possible some cache file - not sure.