How to display dynamically the previous month name

[Deco]

I want to display the previous month name. My code is given below but it displays the index of that month. I want the name of that month. According to this given code it dipslays the tool tip as "Balance up to 9", but I want to display "Balance up to September".How get the name of that month?\[code\]lblPreviousBalance.ToolTip = "Balance up to " + (DateTime.Now.Month - 1);\[/code\]