Conflict between `booktabs` and `arydshln` packages

Question

Please see the MWE below and its result. I didn't use the arydshln package in the example, but I have to use it somewhere else in the same document. As you see, there is something wrong with the vertical border lines in the table. If I don't use one of the arydshln and booktabs packages, it displays correctly.

Is there any workaround here? I'm looking for one of the following:

1. A method to prevent the wrong display with both packages used.
2. An alternative to the nice formatting and \toprule, \midrule, and \bottomrule from the booktabs package.
3. An alternative to the arydshln package to draw dashed lines in math arrays (vectors, matrices).

Thank you for the help.

\documentclass{article}

\usepackage{booktabs}
\usepackage{arydshln}

\begin{document}

\begin{tabular}{ c | r r }
\toprule
    & 123 & 456 \\
\midrule
    \multicolumn{3}{l}{blah blah blah }\\
\midrule
    abc & def & hij \\
\bottomrule
\end{tabular}

\end{document}

ADDED--

After some experiments, I found multicolumn is not a key. When I replaced it by a regular row, it still displays wrong.

Answer 1

You could try the easybmat package, which makes it easy to put dashed lines inside matrices.

Answer 2

ARRAY
If you read the documentation of booktabs, you will see that booktabs does not support vertical lines. You may try the package array and the command extrarowheight. A MWE:

\documentclass{article}

\usepackage{array}
\usepackage{arydshln}
\setlength{\extrarowheight}{3pt}
\begin{document}

\begin{tabular}{ c | r r }
\hline
    & 123 & 456 \\
\hline
    \multicolumn{3}{l}{blah blah blah }\\
\hline
    abc & def & hij \\
\hline
\end{tabular}

\end{document}

TABU
Or you can try the package tabu, which support all types of lines directly.

\documentclass{article}

\usepackage{booktabs,tabu}

\begin{document}

\tabulinesep=1.2mm
\begin{tabu} to .3\columnwidth [c]{X[c] | X[r] X[r]}
\firsthline[3pt]
    & 123 & 456 \\
\tabucline [1pt on 1.5pt off 2pt]{1-3}
    \multicolumn{3}{l}{blah blah blah }\\
\tabucline [1pt on 1.5pt off 2pt]{1-3}
    abc & def & hij \\
\lasthline[3pt]
\end{tabu}

\end{document}