can't dotnet run x86 at x64 on net8

[NCLnclNCL]

Description

I use dotnet run -a x86
however it returns error, if i use dotnet build -a x86 it can build successfully
if i target to net7 or net6, it tool cannot run with same errors

Reproduction Steps

dotnet run -a x86 and target net 8 preview5

Expected behavior

run successfully

Actual behavior

return errors Failed to load the dll from [D:\dotnet-sdk-8.0.100-preview.5.23303.2-win-x64\host\fxr\8.0.0-preview.5.23280.8\hostfxr.dll], HRESULT: 0x800700C1
The library hostfxr.dll was found, but loading it from D:\dotnet-sdk-8.0.100-preview.5.23303.2-win-x64\host\fxr\8.0.0-preview.5.23280.8\hostfxr.dll failed

• Installing .NET prerequisites might help resolve this problem.
  https://go.microsoft.com/fwlink/?linkid=798306

Regression?

No response

Known Workarounds

No response

Configuration

net8 preview5
window 10 2009
x64

Other information

No response

[ghost]

Tagging subscribers to this area: @vitek-karas, @agocke, @VSadov
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

I use dotnet run -a x86
however it returns error, if i use dotnet build -a x86 it can build successfully

Reproduction Steps

dotnet run -a x86 in target net 8 preview5

Expected behavior

run successfully

Actual behavior

return errors Failed to load the dll from [D:\dotnet-sdk-8.0.100-preview.5.23303.2-win-x64\host\fxr\8.0.0-preview.5.23280.8\hostfxr.dll], HRESULT: 0x800700C1
The library hostfxr.dll was found, but loading it from D:\dotnet-sdk-8.0.100-preview.5.23303.2-win-x64\host\fxr\8.0.0-preview.5.23280.8\hostfxr.dll failed

• Installing .NET prerequisites might help resolve this problem.
  https://go.microsoft.com/fwlink/?linkid=798306

Regression?

No response

Known Workarounds

No response

Configuration

net8 preview5
window 10 2009
x64

Other information

No response

Author:	NCLnclNCL
Assignees:	-
Labels:	area-Host
Milestone:	-

[hez2010]

It seems that you are trying to run your program with x86 architecture while you only have x64 dotnet runtime installed.

[elinor-fung]

@NCLnclNCL as @hez2010 pointed out, you'll need the x86 version of .NET installed. Can you install the x86 version of .NET and try again?

We do have an open issue around trying to detect the architecture mismatch case for better error messaging:

• Bad error message when DOTNET_ROOT is set to x86 install of dotnet #3745

[ghost]

This issue has been marked needs-author-action and may be missing some important information.

[vitek-karas]

In this case it seems to be exaggerated by the fact that the SDK is running from a private install, so there's very likely DOTNET_ROOT set to point to the x64 install. To make this work in a private install, you would need to install x86 runtime into another location and set DOTNET_ROOT_X86 to point to that location. Then dotnet run -a x86 should work even when running it from the x64 SDK.

Note that if you were using globally installed SDK/Runtime there's no need to set any env. variable as the location of the runtime for each architecture is written in registry and the app will find it from there. That's probably why it works just fine for .NET 6/7 as you're likely using the global install in that case.

[agocke]

Closed as dup of #3745