Safest way to run BAT file from Powershell script

I can not get a powershell script to execute a bat file directly. For example, this works on the command line:

.\\my-app\my-fle.bat

When I add this command to a script, it outputs:

The term '.\\my-app\my-file.bat' is not recognized as the 
name of a cmdlet, function, script file, or operable program. 
Check the spelling of the name, or if a path was included, 
verify that the path is correct and try again.

I also tried the following, with the same result:

& .\\my-app\my-fle.bat
& ".\\my-app\my-fle.bat"
\my-app\my-fle.bat
& \my-app\my-fle.bat
& "\my-app\my-fle.bat"

Note: It must return the lastexitcode as I need to verify success of batch.

cmd.exe /c '\my-app\my-file.bat'

To run the .bat, and have access to the last exit code, run it as:

 & .\my-app\my-fle.bat

Try this, your dot source was a little off. Edit, adding lastexitcode bits for OP.

$A = Start-Process -FilePath .\my-app\my-fle.bat -Wait -passthru;$a.ExitCode

add -WindowStyle Hidden for invisible batch.

Assuming my-app is a subdirectory under the current directory. The $LASTEXITCODE should be there from the last command:

.\my-app\my-fle.bat

If it was from a fileshare:

\\server\my-file.bat

You can simply do:

Start-Process -FilePath "C:\PathToBatFile\FileToExecute.bat" -ArgumentList $argstr -Wait -NoNewWindow

Here,

ArgumentList - to pass parameters or parameter values if needed by bat file

Wait - waits for the process(bat) to complete

NoNewWindow - starts the new process in the current console window.