Note that when you map XML schema to C#, it is recommended to map this to class inheritance. As per my understanding, you want to copy extended properties to generated classes however I don’t think you can find any tool to achieve this.
I think this should be handled by transforming XML schema to a structure that you want and then use the schema to C# tool. One of the most common way to perform this is via XSLT.
XSL (eXtensible Stylesheet Language) is a styling language for XML and it stands for XSL Transformations. XSLT provides the ability to transform XML data from one format to another automatically.
To know more about XSLT, you can refer our tutorial −
Below are the advantages of using XSLT −
Independent of programming. Transformations are written in a separate xsl file which is again an XML document.
Output can be altered by simply modifying the transformations in xsl file. No need to change any code. So Web designers can edit the stylesheet and can see the change in the output quickly.