Of course you can get married. I know of no such thing as a special rule for transgender people. However, if you're in a place where homosexual marriage is not permitted, if you are legally the same gender as your partner, you can't. Then you'd need to change your legal gender (which requires anything from letters to full SRS depending on the country) before marrying then. Some places have crossbearer-friendly alternatives like de facto unions and civil partnerships, though, which are often very similar to marriage, except without the word, so people can't say things like "marriage is the union of a man and a woman".