  Let $R$ be a Noetherian ring and let $C$ be a semidualizing $R$-module. In
this paper, we are concerned with the tensor and torsion product of
$C$-injective modules. Firstly, it is shown that the tensor product of any two
$C$-injective $R$-modules is $C$-injective if and only if the injective hull of
$C$ is $C$-flat. Secondly, it is proved that $C$ is a pointwise dualizing
$R$-module if and only if $Tor^R_i(M,N)$ is $C$-injective for all $C$-injective
$R$-modules $M$ and $N$, and all $ i \geq 0$. These results recover the
celebrated theorems of Enochs and Jenda \cite{EJ2}.
