New Post: no outgoing dirEdge found

Use NetTopologySuite for your geometry operations. It is more robust.
DotSpatial.Topology has been derived from NetTopologySuite when it was at version 1.7. NetTopologySuite is now at version 1.13.3, version 1.14 will be released soon.
You can get a conversion nuget package (http://www.nuget.org/packages/NetTopologySuite.DotSpatial.Converter/) for the conversion of geometries vice versa. It is a code only so you should be able to use it without any hustle.