Hi Pawan,
Thank you for contacting Syncfusion Support.
Please ensure whether you are referring the dll in separate folder or build location(..lib/UWP). While running in Xamarin.Forms.UWP when you refer dll from the separate folder other than build location, you must add theme files along with the respective dll.
List of files to be added are
1.Syncfusion.SfInput.UWP(Theme file folder)
2.Syncfusion.SfShared.UWP(Theme file folder)
3.Syncfusion.SfInput.UWP.dll
4.Syncfusion.SfShared.UWP.dll
5.Syncfusion.SfNumericUpDown.Forms.dll
6.Syncfusion.SfNumericUpDown.Forms.UWP.dll
We have created sample using SfNumericUpDown control for your convenience and you can download the same from the following link.
Link:
http://www.syncfusion.com/downloads/support/forum/128587/ze/NumUpDown1423620214
Please let us know if you have any concern on this.
Regards,
Vanaja R.A