Using regular expression on a variable

 I need a regular expression to strip out all characters after a "-".

So for example here is my code:
 
Dim RefNo As String = "SPIR2X-B36"

Dim Result As String

' Regular expression code goes here and sets new value for Result variable

Label1.Text = Result 
So the Result variable in this case should be set to SPIR2X. If the RefNo was 12AZ-12R, then the Result variable would be set to 12AZ.

What code can I use to apply a regular expression to my RefNo variable? ...