Windows CMD: Add Suffix to all files in folder

As others told, it lies in the way ren interprets wildcards, that's why it can't find files that contains dots *.* in second command, because:

You not only removed file extension using first command, but also dots before the extensions:

Artikelnummer.cs > Artikelnummer

And your second command is looking for filenames containing . (which there's none!):

ren *.*

Also consider ren uses * to refer to file name, so when you look for *.* (any name, any extension) you're using * to refer to filename and extension at the same time, which is confusing to ren command!

So, the conclusion is, the only problem was *.*, replace it with *:

ren *.cs *.DO.cs
ren * *DO.cs

However, if you want to rename by running a single line of code:

for /f "tokens=* delims=" %a in ('dir /b "%FilesLocation%"') do if %~xa EQU .cs ren "%a" "%~naDO.cs"

Or save and run this script:

@echo off
for /f "tokens=* delims=" %%a in ('dir /b "%FilesLocation%"') do if %%~xa EQU .cs ren "%%a" "%%~naDO.cs"

And don't forget to change %FilesLocation% with it's real value.

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