How do I add the namespace Properties?

How do I save/set the the values of a setting in sharpdevelop?

I've the Settings template from the add item option but when I try to use the Properties namespace like setting = Properties.Settings.Default.MySettingString; and Properties.Settings.Default.Save(); I get and error The name 'Properties' does not exist in the current context (CS0103).

How do I solve this... please help

I'm using

SharpDevelop Version : 5.1.0.5216-0e58df71

.NET Version         : 4.7.02053