Hello Min,

Thank you for posting in our forum.

I followed the steps you suggested and was unable to reproduce the behavior you're describing. I have create a class MyDockManager which inherits from UltraDockManager. I have added MyDockManager component to my form and set its SaveSettings property to true. Then I have run my application and observed no errors.

I have attached the sample project I used to test this.  Please test this project on your PC; whether or not it works correctly may help indicate the nature of this issue.

If the project does not work correctly, this indicates either an issue possibly specific to your environment, or a difference in the DLL versions we are using.  My test was performed using version 15.1.20151.2132 in Infragistics for Windows Forms 2015 Volume 1. So could you please let me know the exact version of Infragistics components which you are using?

If the project does show the product feature working correctly, this indicates a possible issue in the code of your application. It will help if you can provide a small, isolated sample application that demonstrates the behavior you are seeing, or, if this sample project is not an accurate demonstration of what you're trying to do, please feel free to modify it and send it back.