How to fill a TVector from a TMatrix?

what is the best way to fill the entries of a TMatrix into a TVector?
I would like to do something like this

TMatrix M(m,n);
... fill M with some values ...
TVector v(m*n,M);

and then v should have the same entries as M. Is this possible without “manually” copying the values?

:confused: Actually such a constructor really exists
it is

TMatrixD M(3,3);
... fill some values ...
TVectorD V(9,M.GetMatrixArray());