Different delimiters for \parencite and \textcite

Question

My university unfortunately has very strange citing guidelines. Thus I need to change the delimiters for citations in quotes only (e.g. parencite) to a slash. Normal citations (\textcite) and the bibliography should not be affected by the changes. Also citations with more than 3 authors should remain with "et. al.".

Text citations need to look as following:

• \textcite: Hsu, Chan und Moll (2013)
• \parencite: (Hsu/Chan/Moll, 2013)

I already searched for a solution but only found ways to change different aspects, however not the delimiter. Unfortunately, I'm not as experienced with the macros to find a solution by myself. The bibliography delimiters should also not be changed, there I already managed to implement the required guidelines from my university.

Thank you :)

Here is my MWE:

\documentclass[12pt, fleqn]{scrreprt}

\usepackage[utf8]{inputenc}
\usepackage[english,main=ngerman]{babel}
\usepackage[ backend=biber, indexing=cite, citestyle=authoryear, bibstyle=authoryear, isbn=false, firstinits=true, language=ngerman, natbib=true, maxbibnames=99, maxcitenames=3
    %url=false
]{biblatex}
\bibliography{example}

\DefineBibliographyStrings{ngerman}{%
  andothers ={et\addabbrvspace al\adddot},
  andmore ={et\addabbrvspace al\adddot},
}

\renewcommand*{\labelnamepunct}{\addcolon\space}
\DeclareFieldFormat{journaltitle}{{#1}}
\DeclareFieldFormat{issuetitle}{{#1}}
\DeclareFieldFormat{maintitle}{{#1}}
\DeclareFieldFormat{booktitle}{{#1}}
\DeclareFieldFormat
  [article,inbook,incollection,inproceedings,patent,thesis,unpublished]
  {title}{{#1\isdot}}
\usepackage{xpatch}
\xpretobibmacro{author}{\begingroup\itshape}{}{}
\xapptobibmacro{author}{\endgroup}{}

\begin{document}

2 Authors:

Parentcite: \parencite{gencc.2015}

Textcite: \textcite{gencc.2015}


3 Authors:

Parentcite: \parencite{hsu.2013}

Textcite: \textcite{hsu.2013}

Multiple Authors:

Parentcite: \parencite{gibbs.2015}

Textcite: \textcite{gibbs.2015}

\newpage
\addcontentsline{toc}{chapter}{Literaturverzeichnis}
\printbibliography[title=Literaturverzeichnis]

\end{document}

example.bib:

 @article{gencc.2015,
  title={A fact or an illusion: Effective social media usage of female entrepreneurs},
  author={Gen{\c{c}}, Merve and {\"O}ks{\"u}z, Burcu},
  journal={Procedia-Social and Behavioral sSciences},
  volume={195},
  pages={293--300},
  year={2015},
  publisher={Elsevier}
}

@article{hsu.2013,
  title={The effects of blogger recommendations on customers’ online shopping intentions},
  author={Hsu, A and Chuan, Judy and Moll, Hsiu-Sen},
  journal={Internet Research},
  volume={23},
  number={1},
  pages={69--88},
  year={2013},
  publisher={Emerald Group Publishing Limited}
}

@article{gibbs.2015,
  title={\# Funeral and Instagram: death, social media, and platform vernacular},
  author={Gibbs, Martin and Meese, James and Arnold, Michael and Nansen, Bjorn and Carter, Marcus},
  journal={Information, Communication \& Society},
  volume={18},
  number={3},
  pages={255--268},
  year={2015},
  publisher={Taylor \& Francis}
}

Answer 1

This is a job for \DeclareDelimFormat. With

\DeclareDelimFormat[parencite]{multinamedelim}{\slash}
\DeclareDelimAlias*[parencite]{finalnamedelim}{multinamedelim}

you only change the multinamedelim (delimiter between two names) and finalnamdelim (delimiter between the last two names) for \parencite. Everything else remains as before.

I modernised your code a bit, removed unnecessary braces and corrected some bibliographic data, you may want to double-check the accuracy of your .bib entries.

\documentclass[12pt, fleqn, bibliography=totoc]{scrreprt}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,main=ngerman]{babel}
\usepackage{csquotes}
\usepackage[backend=biber, style=authoryear,
  giveninits=true, uniquename=init,
  maxbibnames=99, maxcitenames=3,
  isbn=false,
  natbib=true,
  indexing=cite,
]{biblatex}


\DeclareDelimFormat[parencite]{multinamedelim}{\slash}
\DeclareDelimAlias*[parencite]{finalnamedelim}{multinamedelim}

\DefineBibliographyStrings{ngerman}{%
  andothers    = {et\addabbrvspace al\adddot},
  andmore      = {et\addabbrvspace al\adddot},
  bibliography = {Literaturverzeichnis},
  references   = {Literaturverzeichnis},
}

\DeclareDelimFormat[bib]{nametitledelim}{\addcolon\space}

\DeclareFieldFormat{journaltitle}{#1}
\DeclareFieldFormat{issuetitle}{#1}
\DeclareFieldFormat{maintitle}{#1}
\DeclareFieldFormat{booktitle}{#1}
\DeclareFieldFormat
  [article,inbook,incollection,inproceedings,patent,thesis,unpublished]
  {title}{#1\isdot}


\usepackage{xpatch}
\xpretobibmacro{author}{\begingroup\itshape}{}{}
\xapptobibmacro{author}{\endgroup}{}

%\DeclareNameWrapperFormat{author}{\mkbibemph{#1}}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
 @article{genc.2015,
  title   = {A fact or an illusion: {Effective} social media usage of female entrepreneurs},
  author  = {Genç, Merve and Öksüz, Burcu},
  journal = {Procedia-Social and Behavioral Sciences},
  volume  = {195},
  pages   = {293--300},
  year    = {2015},
}
@article{hsu.2013,
  title   = {The effects of blogger recommendations on customers' online shopping intentions},
  author  = {Hsu, Chin‐Lung and Chuan‐Chuan Lin, Judy and Chiang, Hsiu‐Sen},
  journal = {Internet Research},
  volume  = {23},
  number  = {1},
  pages   = {69--88},
  year    = {2013},
}
@article{gibbs.2015,
  title   = {\#Funeral and {Instagram}: death, social media, and platform vernacular},
  author  = {Gibbs, Martin and Meese, James and Arnold, Michael
             and Nansen, Bjorn and Carter, Marcus},
  journal = {Information, Communication \& Society},
  volume  = {18},
  number  = {3},
  pages   = {255--268},
  year    = {2015},
}
\end{filecontents}

\addbibresource{\jobname.bib}

\begin{document}
2 Authors:
Parentcite: \parencite{genc.2015}
Textcite: \textcite{genc.2015}

3 Authors:
Parentcite: \parencite{hsu.2013}
Textcite: \textcite{hsu.2013}

Multiple Authors:
Parentcite: \parencite{gibbs.2015}
Textcite: \textcite{gibbs.2015}

\printbibliography
\end{document}