Old VB function Old Usage Method of String Class New Usage
Ucase s2 = Ucase(s1) ToUpper s2 = s1.ToUpper
LCase s2 = Lcase(s1) ToLower s2 = s1.ToLower
Trim s2 = Trim(s1) Trim s2 = s1.Trim
Len n = Len(s1) Length n = s1.Length

Table 1 Go With the Object-Based Approach.
Over the last three years, I've gradually replaced the classic VB syntax with the .NET syntax. The performance differences aren’t typically a big deal for these particular functions, but the .NET version is preferable in most cases for its readability and object-oriented approach. For each of the code examples, assume we have declared the variables, s1, s2, and n:

Dim s1 As String = "   ABCDEFabcdef   "
Dim s2 As String
Dim n As Integer

Note that .NET's Trim method includes more functionality than the method it replaces.