In chromyl chloride, $\mathrm{CrO}_2\mathrm{Cl}_2$, the oxidation state of chromium can be calculated by assigning oxidation states to the other atoms in the molecule and then using the fact that the sum of the oxidation states in a molecule must be equal to zero.

The oxidation state of oxygen is usually -2 and the oxidation state of chlorine is usually -1.

Therefore, we can write:

$$\mathrm{Cr} + 2\mathrm{O}(-2) + 2\mathrm{Cl}(-1) = 0$$

Simplifying the equation, we get:

$$\mathrm{Cr} - 4 - 2 = 0$$

$$\mathrm{Cr} - 6 = 0$$

$$\mathrm{Cr} = +6$$

Therefore, the oxidation state of chromium in chromyl chloride is $(+6)$.