Contrary to the opinion of my predecessor
(at least as far as our writeups are arranged), I certainly do not agree with Xenophon's classification as a philosopher
(and I have yet to see one serious book or researcher to define him as such).
Xenophon was a historian and one of the many propagandists of the aristocratic circles of Greece in general and of Athens in particular (even though he did not live in Attica for the majority of his adult life, and was forbidden to enter any territory belonging to the Athenian polis for much of that time, after being charged and convicted in absentia of treason, after enlisting to the Spartan army in a war between Sparta and Athens), as well as being the chief propagandist for Spartan supremecy in Greece.
All of the aforementioned books (even his supposedly factual ones) are meant to exemplify and show how a state governed by a small circle of well bred kaloi k'agathoi, is far superiour to any other form of government. Xenophon did not avoid ommiting or changing facts that were not in support with his theories (for example, in his Hellenika there is not one word concerning the battle of Leuctra, one of the most important battles of his days, because this battle ended the Spartan hegemony in Greece, and started the Theban one. We found out about the battle of Leuctra only accidentally, from a papyrus found in Egypt).
All of his books are one long praise to Sparta and to oligarchy. He discusses horsemanship and hunting, because he considers these a proper way for an aristocrat to spend his time, he discribes Socrates as a perfect example of a nobleman, and uses his trial and consequent execution to present democracy as an evil sort of government. His discussions of 'moral' are no more than talks about the proper ways for an aristicrat to behave (one must remember that at that time ethics as a philosophical branch was barely created, so Xenophon, being outside Athens at the times of the molding of this field, could not be really discussing ethics).
As for his Apology of Socrates, Xenophon was not even in Athens when Socrates' trial was held (He was near the Black Sea at the time), all he could write was hearsay, and regarding the relations between his and Plato's Symposium, Plato did not need to 'correct' what Xenophon was writing, both were making up the entire scenario, Plato in order to illustrate his ideas about the meaning and essence of 'Love', and Xenophon in order to present Socrates as a righteous nobleman.
Much of the importance of Xenophon (if not the vast majority of it) derives from the facts that:
a) His Greek is relatively easy, simple, and resembles some modern languages in structure, which makes him ideal for beginners in Greek.
b) We do not have any other full text relating the history of the 4th century BCE, so despite his inaccuracies and inconsistancies when truth is concerned, we must settle for him.