Hi Samuel,
Thank you for writing and for the code snippets.
I have attached a sample project where I tried to replicate your scenario. I changed the type your editor inherits from BaseInputeEditor to PropertyGridDropDownListEditor. This way you would have more functionality and not have to implement it yourself. I have also moved your logic from the Value property to the Initialize method override. One thing left unresolved and that is what is the type of the property in the property grid. You have to return a value with the same type from the editor but I couldn't figure out what the type of the "TestSam" property is. For the example I have made it a string, so the editor can edit it. This is needed, because you have to set a ValueMember for the drop down editor element. You have set the DisplayMember, but you have not set the this way you won't be able to set the SelectedValue of the editor element.
I hope this example will help you. If you need further assistance, I would be glad to provide it.
Greetings,
Ivan Petrov
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.