Is there any function(other than replace) which converts the text escape character like line feed or tab feed to there corresponding html escape character like &nbsp or <br />.
I want touse it in asp.net page label control to view the data user had entered through multiline textbox.(C#)

Nope. There is the HtmlEncode method on the server class, but this is only for encoding characters that would break HTML ( < > & etc). There is nothing illegal about a tab or linefeed character. If that data has some meaning to you (as you indicate it does because you wish to replace it with HTML representations) then you'll have to replace them manually.

-Peter