ASP .NET form element naming conventions

[paul.hester]

Hi all,

I can't find a consistent naming convention rule for form elements
and/or server controls with ASP .NET 2.0.

What conventions do you generally use? For example, for a user name
text input element, would you use:

txtUserName?
UserName?
userName?
_userName?
user_name?

Or, are all of the above perfectly acceptable from a naming convention
standpoint?

Thanks,

Paul