Aspnetcore: Blazor WASM - Debug (vs code and vs preview) Unable to attach to the browser

[dominiclapointe]

Describe the bug

Creating a new project (in vs preview or with dotnet new) using the latest blazor template. Press F5 once created result in Unable to attach to the browser.

To Reproduce

VS CODE

1. Create a new project => dotnet new blazorwasm -o test1
2. Open the project in VsCode
3. Run .NET Core Launch (Blazor Standalone)
4. Run .NET Core Debug Blazor WebAssembly in Chrome
5. Chrome open and after a few second a popup in VsCode => Unable to attach to the browser

Vs 2019 Preview

1. Create a new project Blazor Wasm (not core hosted)
2. Press F5
3. Get a popup in VS => One or more error occured. Failed to launch debug adapter. Unable to attach to the browser.
   

   Further technical details

   • ASP.NET Core version : not sure how to get asp.net version
   • Include the output of dotnet --info L
     .NET Core SDK (reflecting any global.json):
     Version: 3.1.300-preview-015135
     Commit: 0b3c572e97

   Runtime Environment:
   OS Name: Windows
   OS Version: 10.0.18363
   OS Platform: Windows
   RID: win10-x64
   Base Path: C:\Program Files\dotnet\sdk3.1.300-preview-015135\

   Host (useful for support):
   Version: 3.1.3
   Commit: 4a9f85e9f8

   .NET Core SDKs installed:
   2.1.700 [C:\Program Files\dotnet\sdk]
   2.1.802 [C:\Program Files\dotnet\sdk]
   2.2.300 [C:\Program Files\dotnet\sdk]
   2.2.402 [C:\Program Files\dotnet\sdk]
   3.0.101 [C:\Program Files\dotnet\sdk]
   3.1.100 [C:\Program Files\dotnet\sdk]
   3.1.201 [C:\Program Files\dotnet\sdk]
   3.1.300-preview-015048 [C:\Program Files\dotnet\sdk]
   3.1.300-preview-015135 [C:\Program Files\dotnet\sdk]

   .NET Core runtimes installed:
   Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.All 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.All 2.1.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.All 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
   Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 2.1.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 3.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.AspNetCore.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
   Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 2.1.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 3.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.NETCore.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
   Microsoft.WindowsDesktop.App 3.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
   Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
   Microsoft.WindowsDesktop.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
   Microsoft.WindowsDesktop.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
   - The IDE (VS / VS Code/ VS4Mac) you're running on, and it's version
   1. VsCode 1.45
   2. Vs 2019 16.6.0 preview 6.0

[dominiclapointe]

IT seem to be some kind of proxy issue. I managed to get it working in VS 2019 Preview by adding NO_PROXY localhost to my env var. ITs not yet working with VS Code tough.

[dominiclapointe]

Finally found out it was some weird setup of our proxy or how vs handle proxy setting.

To have VSCODE working i had to set NO_PROXY with 127.0.0.1 and to have VS 2019preview i had to et NO_PROXY localhost...

Why is it trying to use the proxy to get access to localhost??

[HKBoy]

Hi @dominiclapointe . I faced the same issue in VS 2019 Preview. Would you be kind enough to show me how to set the Env Var? Thank you