Access to the path 'C:\Windows\TEMP\xxx.tmp' is denied.

System.UnauthorizedAccessException: Access to the path 'C:\Windows\TEMP\ASPNETCORE_935a19f1-814f-4b33-831d-7c6a7b988e43.tmp' is denied.
   at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
   at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize)
   at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize)
   at System.IO.Strategies.FileStreamHelpers.ChooseStrategyCore(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize)
   at System.IO.Strategies.FileStreamHelpers.ChooseStrategy(FileStream fileStream, String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, Int64 preallocationSize)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
   at Microsoft.AspNetCore.WebUtilities.FileBufferingReadStream.CreateTempFile()
   at Microsoft.AspNetCore.WebUtilities.FileBufferingReadStream.ReadAsync(Memory`1 buffer, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.WebUtilities.StreamHelperExtensions.DrainAsync(Stream stream, ArrayPool`1 bytePool, Nullable`1 limit, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Http.Features.FormFeature.InnerReadFormAsync(CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Http.Features.FormFeature.ReadForm()
   at Microsoft.AspNetCore.Http.DefaultHttpRequest.get_Form()

找到项目的应用程序池，将高级设置中“加载用户配置文件”（Load User Profile）设置为true即可。