Hi Annie,
Thank you for your interest in Syncfusion Products.
I have tested this issue with a simple sample[assembly version 4.202.0.37]. I am afraid that I was not able to reproduce the issue. Please refer to the following simple sample in which I have tested this issue:
http://websamples.syncfusion.com/samples/Tools.Windows/F77088/Tools_WF_WindowFill.zipPlease try the above sample, if I am missing anything, could you please modify and send the sample, so that I could trace out the cause of the issue and provide you the better solution at the earliest?
Please let me know if any concerns.
Regards,
Hema