Code is not compiling. Error : Error 1 No overload for method 'RuleSetDialog' takes '3' arguments C:\Windows Workflow Foundation\Examples\ExternalRuleSetToolkit\2006-03-23\RuleSetTool\RuleSetEditor.cs 794 51 RuleSetTool If we delete null and compile, we will get another error Error 1 The best overloaded method match for 'System.Workflow.Activities.Rules.Design.RuleSetDialog.RuleSetDialog(System.Workflow.ComponentModel.Activity, System.Workflow.Activities.Rules.RuleSet)' has some invalid arguments C:\Windows Workflow Foundation\Examples\ExternalRuleSetToolkit\2006-03-23\RuleSetTool\RuleSetEditor.cs 794 51 RuleSetTool

Rami, What version of WF are you using? I am compiling against the Beta 2.2 release (included in the May Beta 2 of WinFX) and I am not seeing that behavior. I also have that sample working on a machine with an RC build of WF.

We are considering using XAML for presentation layer in our application. Can the RuleSetEditor be used for cross field validation and display characteristics for a XAML app?

You could use WF rules to validate fiels in a WPF application. Take a look at the rules sample: Rules Driven UI, which shows how you can do that from a windows forms application. You could do the same thing with a WPF app. If you do, please post a sample of it!