Dinesh, users on the forum here might be better able to assist if you can give some context as to what causes the error and your software version.
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What version of OpenRoads Designer are you using?
What is the exact command or operation you are using when this error appears?
My first thought would be that you are trying to attach a DGN file (or some other file format) as a reference/raster and the formatting isn't a proper DGN format. But it will be good to get as much information and detail to what you are experiencing so users with similar experience can provide suggestions.
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