Parsing property attributes

 When setting many property types on controls, they can be given in string format:
e.g. for font properties, one can have Font="Trebuchet MS, 14.25pt, style=Bold"
and similarly for Color properties, which can be expressed either as a name or as "a,r,g,b" etc
My question is, how can i implement the parsing from string for properties whose type is my own objects?
Thanks
Tom
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