Actuall, String.Trim can throw an exception. Consider the following:
 Dim foo As String
 Console.WriteLine(foo.Trim)

In this case foo is not instanced and thus we try to Trim Nothing. Since
string is an object not a value type, it is not initiated by default and
thus can be null/nothing. Because of this, I always check for nothing on
my strings passed into to methods as parameters before processing them. (if
value = nothing then value = string.Empty). This is particularly noticable
when binding a Combobox's SelectedValue to string property of an object.

You are correct that the TextBox.Text can not pass back nothing, thus in
the OP's code, it will not throw an exception. Furthermore, relying on exceptions
when you can pre-test for a condition is akin to peeing your pants to see
if the fly is unzipped. Thus, checking to see if txtTitle.Text.Trim=String.Empty
is much better than using exceptions and try..catch blocks anyway.

Jim Wooley
http://devauthority.com/blogs/jwooley/default.asp

I would use:

If not txtTitle.Text is nothing andalso txtTitle.Text.Trim.Length<=0 then
  'do something if true
end if