if i use this command "<input type="hidden"" in my dotnet (.Net) site then is ok or is it going to black SEO? is this command hurt my ranking?
I don't know what exactly this do ... as i dnt know much about this ... but if this command hide something from user and show that to google boot then yes this is Black SEO !!
IMHO, using hidden input fields isn't a black hat or frowned upon practice. Using hidden text is a frowned upon by the engines. Hidden input forms fields are provided in HTML to help persist information across pages. Go ahead use as many hidden form fields as you need. There isn't any SEO issue related to them that I have heard of or know. As long as you aren't hiding text from users, you are fine.
This will not cause you any problems with google or any other SE. HIDDEN form fields are used for a number of things like tracking sessionID and user information that is required to be seen by the web site user.