So, previously I’d described using a Web Part Property of an ArrayList to store a list of things. In that demo, I’d been just storing strings.

Well, my requirements got a little more complex, so I started trying to store my own objects in there – really, just objects storing data, no logic. However, when I added things to the property and ran .SetPersonalizationDirty() my data wasn’t saved. Worse, the values of other (unchanged) web part properties were lost! They kept coming through as null, rather than the values I’d set previously. There was no indication of error.

Well, here is Andy’s tip for folks who manage to forget the basics of C# development – don’t forget the [Serializable] attribute.

Without it, my data objects can’t, well, be serialized – that is, saved. So it’s unsurprising that my data wasn’t saved! What was unfortunate and threw me off the sent was that there were no errors shown, and that wiping out the values of the other web part properties did rather thrown me off the scent! I guess I was really having an off day when I wrote that…