  A measurement of the forward--backward asymmetry of $e^{+}e^{-} \to c\bar{c}$
and $e^{+}e^{-} \to b\bar{b}$ on the $Z$ resonance is performed using about 3.5
million hadronic $Z$ decays collected by the DELPHI detector at LEP in the
years 1992 to 1995. The heavy quark is tagged by the exclusive reconstruction
of several $D$ meson decay modes. The forward--backward asymmetries for $c$ and
$b$ quarks at the $Z$ resonance are determined to be: \[
\renewcommand{\arraystretch}{1.6} \begin{array}{rcr@{}l} \Afbc(\sqrt{s} =
91.235 {\rm GeV}) &=& &0.0659 \pm 0.0094 (stat) \pm 0.0035 (syst) \Afbb
(\sqrt{s} = 91.235 {\rm GeV}) &=& &0.0762 \pm 0.0194 (stat) \pm 0.0085 (syst)
  \Afbc(\sqrt{s} = 89.434 {\rm GeV}) &=&-&0.0496 \pm 0.0368 (stat) \pm 0.0053
(syst) \Afbb(\sqrt{s} = 89.434 {\rm GeV}) &=& &0.0567 \pm 0.0756 (stat) \pm
0.0117 (syst) \Afbc(\sqrt{s} = 92.990 {\rm GeV}) &=& &0.1180 \pm 0.0318 (stat)
\pm 0.0062 (syst) \Afbb(\sqrt{s} = 92.990 {\rm GeV}) &=& &0.0882 \pm 0.0633
(stat) \pm 0.0122 (syst) \end{array} \] The combination of these results leads
to an effective electroweak mixing angle of: SINEFF = 0.2332 \pm 0.0016
