why its deactivate my player and not the trail ??
Post some more of your code so we can get a better picture.
Component.active is deprecated and should not be used with COMPONENTS. Component.active is/was a shortcut for "GameObject.active", hence if you have read the documentation (or MonoDevelop tooltips or the compiler warnings) you would know that this property is not listed in the docs and deprecated in MonoDevelop.
Only "Component.enable" is documented and the only one which should be used, but that's something that the warning tells you too iirc.
Thanks. So I can activate..How can I deactivate the trail?
Did you even read what I said? Component.active should not be used with Components, only with GameObjects. It's deprecated.
To enable/disable a component, you must use Component.enable (set it to true to enable and false to disable)