Hi Johnes,
Thank you for your interest in Syncfusion products.
To avail the ExportToExcel method, the Syncfusion.GridConverter.Wpf.dll assembly should be installed in the project. We already have informed the details about the dependent assemblies in our user guide and please refer to the below UG for further details.
Please get back to us if you need any further assistance.
Regards,
Arulpriya Ramalingam