I can't be sure from the description but is your content-type-reader class in your content-pipline-extensions project? If so than that is probably the reason why it can't find it. The content-type-reader has to be available at runtime and thus has to be part of the game project or of one of the linked game library projects. Be sure to update your assembly name when you move your class and also, just to be sure, add spaces after the commas in the string that desribes where the class should be.

I can't be sure from the description but is your content-type-reader class in your content-pipline-extensions project? If so than that is probably the reason why it can't find it. The content-type-reader has to be available at runtime and thus has to be part of the game project or of one of the linked game library projects. Be sure to update your assembly name when you move your class and also, just to be sure, add spaces after the commas in the string that desribes where the class should be.

Edit: to be sure you have to exact QualifiedAssemblyName of a class write this piece of code:

string info = typeof(HeightMapInfoReader).AssemblyQualifiedName;

Of course this only works for a class in the same, or a referenced, assembly so you still have to copy the string in info and put it in the ContentTypeWriter's GetRunTimeReader method harcoded but it makes sure you don't have typo's.