.net 5 File.Create create file incorrect directory , path

[uopeydel]

Describe the Bug

I try to create file in docker container. It can create. But create incorrect directory. When create in local(windows) it correct.

Steps to Reproduce

My code to create file is

                        var dir = Directory.GetCurrentDirectory() + "\\wwwroot\\xls_template\\";
                        if (!Directory.Exists(dir))
                        {
                            Directory.CreateDirectory(dir); 
                        }
                        dir = dir + $"xlssave_{DateTime.UtcNow.AddHours(7).ToString("dd_MM_yyyy___HH_mm")}.xlsx"; 
                        using (var fileStream = File.Create(dir))
                        {
                            stream.Seek(0, SeekOrigin.Begin);
                            stream.CopyTo(fileStream);
                        }

My Dockerfile just this .. ** I build+publish by command to target folder instead build in dockerfile. It build correct and can surf all feature that I have correct.

FROM mcr.microsoft.com/dotnet/aspnet:5.0.2-focal-amd64 AS runtime
RUN apt-get update \
    && apt-get install -y --allow-unauthenticated \
        libc6-dev \
        libgdiplus \
        libx11-dev \
     && rm -rf /var/lib/apt/lists/*

WORKDIR /app
COPY PublishFile/* /app/
RUN mkdir wwwroot
RUN cp -avr xls_template/ wwwroot/
RUN ls
RUN pwd
ENTRYPOINT ["dotnet", "SMS.Server.dll","--environment=UAT"]

This image below is happen when I use command exec into docker container is running.
It create my file at '/'

-rw-r--r--. 1 root root 7.2K Jan 31 09:30 'app\wwwroot\xls_template\xlssave_31_01_2021___16_30.xlsx'
-rw-r--r--. 1 root root 7.2K Jan 31 09:31 'app\wwwroot\xls_template\xlssave_31_01_2021___16_31.xlsx'
-rw-r--r--. 1 root root 7.2K Jan 31 09:32 'app\wwwroot\xls_template\xlssave_31_01_2021___16_32.xlsx'
-rw-r--r--. 1 root root 7.2K Jan 31 09:33 'app\wwwroot\xls_template\xlssave_31_01_2021___16_33.xlsx'

this is my file is created.

Other Information

Output of docker version

mcr.microsoft.com/dotnet/aspnet:5.0.2-focal-amd64

[MichaelSimons]

It looks like this is an issue related to Windows and Linux using different path separators - \ vs /. Linux does not detect \ as a valid path separator and therefore treats is as a character in the directory and file names. To make the app cross platform compatible, consider using Path.PathSeparator or Path.Combine to build up the paths.