Created attachment 260176 [details]
Example.

In order to set: 

- Control.AccessibleDefaultActionDescription,
- Control.AccessibleDescription,
- Control.AccessibleName, or
- Control.AccessibleRole

you need to call Control.AccessibilityObject.

Run the attached example: 

gmcs -r:System.Windows.Forms,System,System.Drawing Program.cs -t:exe && mono Program.exe

1. Click: "Print accessible" button, you get the following output:

Button1.AccessibleName: 
Button1.AccessibleDescription : 
Button1.AccessibleDefaultActionDescription: 

2. Click: "AccessibleName is" button, you don't get any output, AccessibleXXX properties are set.
3. Click: "Print accessible" button, you should get the following output:

Button1.AccessibleName: AccessibleName is not empty
Button1.AccessibleDescription : AccessibleDescription is not empty
Button1.AccessibleDefaultActionDescription: AccessibleDefaultActionDescription is not empty

however you are getting the same output as in step 1.