version 8 - What is the most convenient way to change options for Graph[] objects?

What is the most convenient way to change options such as VertexLabels in existing Graph objects? (Version 7 users note: Graph is new in Mathematica 8.)

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With graphics, we can use Show for this, not matter what function was originally used to produce the graphic:

g = Plot[Sin[x], {x, 0, 10}]
Show[g, Axes -> False, Frame -> True]

Is there an analogous function for Graphs? Suppose we already have a graph, and now we need to show vertex labels in a different way.

Here's a workaround using HighlightGraph:

g = Graph[{1 -> 2}]
HighlightGraph[g, {}, VertexLabels -> "Name"]

While it works, this is not really what HighlightGraph is meant for.

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Please note that Graph objects are atomic before trying to take them apart. Also, I'm looking for the safest and most robust solution. I'm hoping there's a function I overlooked.

Answer

You could use SetProperty. For example

g = Graph[{1 -> 2, 2 -> 4, 3 -> 4}]

SetProperty[g, VertexLabels -> {"Name", 2 -> "Two"}]