Address Technical Debt by reviewing the cohesion of the codebase.
Create a DGML file using a tool for reading the source code, for example
DeepEnds ReadDotNet extract=cohesion output=C:\project\cohesion.dgml C:\project\source.sln
Either open the resulting DGML file for viewing in Visual Studio or create a report, for example,
DeepEnds ReportCohesion output=C:\project\cohesion.html C:\project\cohesion.dgml
Where a class can be split into a number of parts do so as it is always better to build a class by composition rather than inheritance.