After marriage name changed

It is your wish, you can use either your maiden surname or your husband's surname.  But it should be tallied with the Aadhaar Card etc.

Adhard card have new name,  but legally changed my name . If I am applying for government job there is obc category, so what should I do

You have changed your name but not your parental surname to determine your caste which would be as maiden.

The name having been changed following the due process, you are required to apply in the name. During verification, old name in documents could be explained on the strength of the Gazette Notification and the Identification Cards with the changed name.

After changing your name through gazette publication you cannot use your previous name, you have affirmed in your name change application that you will henceforth be known as per my new name.

Hence it becomes pertinent that you have to use your new name alone for all purposes in future.