The CreateAppHost task failed unexpectedly. MSB4018

When I try and build my ASP.NET Core project, I continue to get this error message in Visual Studio 2019. When I build it the second time, the error disappears.

Does anyone know what this error means and how to get rid of it?

Thanks!

<CreateAppHost AppHostSourcePath="$(AppHostSourcePath)"
                   AppHostDestinationPath="$(AppHostIntermediatePath)"
                   AppBinaryName="$(AssemblyName)$(TargetExt)"
                   IntermediateAssembly="@(IntermediateAssembly->'%(FullPath)')"
                   WindowsGraphicalUserInterface="$(_UseWindowsGraphicalUserInterface)"
                   Retries="$(CopyRetryCount)"
                   RetryDelayMilliseconds="$(CopyRetryDelayMilliseconds)"
                   />

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Try running visual studio using 'as administrator' option.

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Some of the files which required for complete building may need admin privilege for accessing them. Commonly run Visual Studio has not enough rights to access them

I noticed that my error also noted: System.UnauthorizedAccessException: Access to the path '...\obj\Release\netcoreapp3.1\apphost.exe' is denied.

Deleted the obj folder and rebuild solution resolved the problem for me. Thanks.

I had a similar problem. The error message for my ASP.NET Core application was

error MSB4018: The "CreateAppHost" task failed unexpectedly.
error MSB4018: System.MissingMethodException: Method not found: 'Void Microsoft.NET.HostModel.AppHost.HostWriter.CreateAppHost(...

I tracked the issue down to the environment variable MSBuildSDKsPath, which pointed to an older SDK version. After unsetting the variable with export MSBuildSDKsPath= the problem was resolved. Alternatively, setting the variable to the most recent SDK also worked: export MSBuildSDKsPath=C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\Sdks (just an example).

I don't remember why I set the variable in the first place, and eliminating it didn't seem to hurt either, I just removed it. It seems that in general, it is just not necessary.

The CreateAppHost task failed unexpectedly. MSB4018

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