If you import a solution and then add references to one or more of those components in the default solution, you need to remove those references to successfully delete the solution.
IMPORTANT: After removing the reference, publish customizations for the changes to take effect.
Below are a few common examples:
If the solution you are trying to delete includes a custom entity called Widget and you created a workflow process that references the Widget entity, either delete the workflow (if no longer needed) or update the workflow to remove the reference to the Widget entity. For example: If the workflow includes multiple steps and one of the steps creates or updates a Widget record, remove this step from the workflow and save your changes.
If the solution you are trying to delete includes a custom entity called Widget and you modified your Site Map (navigation) to display this custom entity, you need to remove the reference to this entity from your Site Map before you can successfully delete the solution. If this reference was made in the Default Solution, follow these steps:
1. Navigate to Settings, click Customization, and click Customize the System.
2. Expand Entities.
3. Locate and click on the name of the custom entity.
4. Remove any checkmarks from the Areas that display this entity section.
5. Click Save and then click Publish.
For information about modifying your Site Map, see Change application navigation using the SiteMap.
If the solution you are trying to delete added a custom field (ex. NewField) to the Contact entity and you modified one of the Contact forms to display this field, you need to remove the reference to this field from your form before you can successfully delete the solution.
If the solution you are trying to delete added a custom field (ex. NewField) to the Contact entity and you modified one of the Contact views to display this field, you need to remove the reference to this field from the view before you can successfully delete the solution.
It is possible for a solution to depend on other solutions. For example: Assume you installed an ISV package from Contoso which included multiple solutions. Solution A introduces a new custom entity called Widget and Solution B introduces additional entities as well as some modifications to the Widget entity. Solution B is dependent on Solution A. If you try to delete Solution A before deleting Solution B, the solution will fail to be deleted because of the dependencies.