enumerate item within an custom environment and mdframed

Question

I'm trying to define a custom environment within mdframed for handling questions in a document. The reason for the question-solution structure is to enable parsing into other formats (html etc).

The following code demonstrates my problem; the enumerate does not display properly in mdframed.

I realise there have been related posts but I cannot find a solution to this.

\documentclass[12pt, a4paper]{article}

\usepackage{tikz,pgf}
\usetikzlibrary{shadows}
\usepackage[framemethod=tikz]{mdframed}

\newcounter{exercises}
\def\theexercise{\thesection.\arabic{exercises}}

\newenvironment{exercises1}
{ \refstepcounter{exercises} 
 \begin{enumerate} }
{ \end{enumerate} 
}

\newenvironment{exercises_mdf}
{ \refstepcounter{exercises} 
\begin{mdframed}[backgroundcolor=black!10, frametitle={Exercise \theexercise}]
\begin{enumerate} }
{ \end{enumerate} 
\end{mdframed} 
}

\newenvironment{question}{ \item } { }
\newenvironment{solution}{ \\ {\bf Solution:} \\ }{ }

\begin{document}

\begin{exercises1}
\begin{question} Q1 
\begin{solution} S1 \end{solution}
\end{question}
\begin{question} Q2
\begin{solution} S1 \end{solution}
\end{question}
\end{exercises1}

\begin{exercises_mdf}
\begin{question} Q1 
\begin{solution} S1 \end{solution}
\end{question}
\begin{question} Q2 
\begin{solution} S2 \end{solution}
\end{question}
\end{exercises_mdf}

\end{document}

Answer 1

I find your construct a bit complicate. I always try to avoid so much typing:

\documentclass[12pt, a4paper]{article}
\usepackage{tikz,pgf}
\usetikzlibrary{shadows}
\usepackage[framemethod=tikz]{mdframed}

\newcounter{exercises}
\def\theexercise{\thesection.\arabic{exercises}}


\newenvironment{exercises_mdf}
{ \refstepcounter{exercises} 
\begin{mdframed}[backgroundcolor=black!10, frametitle={Exercise \theexercise}]
\begin{enumerate} }
{ \end{enumerate} 
\end{mdframed} 
}

\newcommand{\qu}{\item}
\newcommand{\sol}{\\\textbf{Solution}\\}

\begin{document}

\begin{exercises_mdf}
\qu Do you know? \sol YES!
\qu What is the answer? \sol 42
\end{exercises_mdf}

\end{document}

Hopefully this is what you want. If not i recommend that you include a picture as @Marco Daniel said.