As Peter has said, the number of lines is insignificant because once the user gets to about the 9th line in your textbox, the scrollbars will become enabled. If you are seriously trying to avoid this, set the MaxLength attribute of your textbox so that the user can never go beyond X point where the scrollbar becomes enabled.
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Read this if you want to know how to get a correct reply for your question:
http://www.catb.org/~esr/faqs/smart-questions.html
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.: Wrox Technical Editor :.
Wrox Books 24 x 7
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