Hi,
Here are some samples you may find useful:
https://developers.arcgis.com/net/wpf/sample-code/sketch-on-map/
https://developers.arcgis.com/net/wpf/sample-code/display-annotation/
https://developers.arcgis.com/net/wpf/sample-code/edit-features-with-feature-linked-annotation/
https://developers.arcgis.com/net/wpf/sample-code/show-labels-on-layers/