Command rejected: An interface whose trunk encapsulation is “Auto” can not be configured to “trunk” mode.

I got this error message during reconfiguration of cisco switch 3560G series.
Before configure a “trunk” mode we have to configure encapsulation.

to solve the problem

(config-if)#switchport trunk encapsulation dot1q
(config-if)#switchport mode trunk

now, everything is good, we can add vlans in this way

(config-if)#switchport trunk allowed vlan add 10