Cleanup code.

Added null check.
Remove interface members which already defined in parent interface.

Update Eexamples. Update project versions. Update referenced packages.

Update packages versions.

Update code formatting.

Update project info

update packages version

update version

Update package reference

Update projects

Merge pull request dncuug#76 from dncuug/net-core-2

Close dncuug#70

Close dncuug#48