VB .NET Remove all non alphanumeric characters can be done easily using regular expression. 
I found it easiest to use regular expression for this, 

System.Text.RegularExpressions.Regex.Replace(stringtochange, "[^a-zA-Z0-9_ .+]", "")

At the end of expression I have added "_ .+" this is just to include these 
characters space + . and _ so that they are not replaced 
with "".