Error Uploading Solution to SharePoint Solution Gallery

If when you upload a solution to the solution gallery in SharePoint 2010 you receive the following error.

“This solution contains invalid markup or elements that cannot be deployed as part of a sandboxed solution. Solution manifest for solution ’64afe4f8-6a99-42e8-9845-43fc18cc49f8′ failed validation, file manifest.xml, line 10, character 4: The element ‘Solution’ in namespace ‘http://schemas.microsoft.com/sharepoint/’ has invalid child element ‘TemplateFiles’ in namespace ‘http://schemas.microsoft.com/sharepoint/’. List of possible elements expected: ‘FeatureManifests, ActivationDependencies’ in namespace ‘http://schemas.microsoft.com/sharepoint/’.

This is probably caused by the fact that there are some features or functionality referenced by the solution, which are not supported in sandboxed environment. Such as the following

• Custom Action groups
• HideCustomAction element
• Content Type Binding
• Web Application-scoped Features
• Farm-scoped Features
• CustomPropertyToolPart Class
• Programmatic workflow
• Event receivers
• timer jobs
• visual WebParts
• SharePoint mapped folders (e.g. “_layouts”, and “images”)

http://technet.microsoft.com/en-us/library/cc262995(office.14).aspx