Public Overloads Sub Set( _
   ByVal property As String, _
   ByVal value As Object _
) 

public void Set( 
   string property,
   object value
)

string result;
CommandInterpreter ci = new CommandInterpreter(DefaultCommands.Echo | DefaultCommands.Prompt, new TestCommands());

ci.Set("SomeData", "TEST_Data");
result = Capture(ci, "ECHO $(SOMEDATA)");
Assert.AreEqual("TEST_Data", result);

ci.Set("SomeData", "TEST Data");
result = Capture(ci, "ECHO $(SOMEDATA)");
Assert.AreEqual("\"TEST Data\"", result); // <= Echo will quote & escape while-space and quotes "

result = Capture(ci, "ECHO $(MissingProperty)");
Assert.AreEqual("Unknown option specified: MissingProperty", result);

result = Capture(ci, "ECHO (MissingProperty) (xx xy  abc"); // <= escape '$' with ''
Assert.AreEqual("$(MissingProperty) $(xx x$y $ abc", result)
' <= extra '$' was removed.