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Default Blazor Client App fails throwing the build error[Blazor][Appbuilding]

See original GitHub issue

I am trying to create an ClientSide Blazor app but I am not even able to build the default blazor app present in the VS

C:\Users\anagniho\source\repos\BlazorApp8>dotnet build
Microsoft (R) Build Engine version 16.3.0-preview-19375-05+42c4c1370 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  Restore completed in 30.65 ms for C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj.
  You are using a preview version of .NET Core. See: https://aka.ms/dotnet-core-preview
obj\Debug\netstandard2.0\RazorDeclaration\Pages\_Imports.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\_Imports.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\FetchData.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\FetchData.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Index.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Index.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Counter.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Counter.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]

Build FAILED.

obj\Debug\netstandard2.0\RazorDeclaration\Pages\_Imports.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\_Imports.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\FetchData.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\FetchData.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Index.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Index.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Counter.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttributeAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
obj\Debug\netstandard2.0\RazorDeclaration\Pages\Counter.razor.g.cs(51,38): error CS0234: The type or namespace name 'LayoutAttribute' does not exist in the namespace 'Microsoft.AspNetCore.Components' (are you missing an assembly reference?) [C:\Users\anagniho\source\repos\BlazorApp8\BlazorApp8.csproj]
    0 Warning(s)
    8 Error(s)

Time Elapsed 00:00:01.21

Selecting the server app question resolves the issue though. is there anything else that needs to be installed for making it work ?

Issue Analytics

  • State:closed
  • Created 4 years ago
  • Comments:19 (6 by maintainers)

github_iconTop GitHub Comments

1reaction
dazinatorcommented, Aug 15, 2019

I hit this issue when using the latest VS 2019 preview 2 to build my solution. My solution was pinned via a global.json file to use sdk preview 7, but I didn’t have sdk preview 7 installed, so the build rolled forward to use sdk preview 8. I have blazor preview 7 dependencies in my dependency graph, and it appears building under preview 8 with preview 7 dependencies, produced this error.

Rather than upgrade everything to preview 8 (some dependencies I use aren’t compiled and released for preview 8 yet and are still on preview 7) I did this to resolve:

  1. Install preview 7 sdk
  2. Ensure all dependencies in my application that target blazor are referencing preview 7 (not 6 or less)
  3. Add a global.json to my solution to pin to preview 7.
  4. run a dotnet build - success.
  5. I had VS open throughout this, a rebuild doesn’t seem to detect sdk 7 was installed and continues to use sdk 8 and fail - restarting VS, and reloading the solution, and then rebuilding - then correctly used sdk 7 and the build succeeded.

I assume this exact same thing can occur each time we go from preview x to preview y - lot of breaking changes at the moment - the build system seems to be very fragile - a bit like goldilocks porridge - everything has to be be “just right” 😃

1reaction
mkArtakMSFTcommented, Aug 14, 2019

@erikbra the package Microsoft.AspNetCore.Components.Browser was renamed to ``Microsoft.AspNetCore.Components.Web`.

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