datatable.select user functions

I've defined a function:

Public Class GeneralFunctions
Function StartsWith(ByVal sStart As String, ByVal sWord As String) As Boolean
Return Strings.Left(sWord, Len(sStart)).Equals(sStart)
End Function
End Class

Trying:
dim a = dt.Select("StartsWith(IssuerName,'abc')")

yields a runtime error: The expression contains undefined function call StartsWith()


Thinking is was a user defined issue I also tried:
dim a = dt.Select("Strings.Left(IssuerName, 1).Equals('B')"

and got: The expression contains undefined function call Strings.Left()

How are functions used in the filter expression of Datatable.Select?

thx

found it:

". . . use the same rules that apply to the DataColumn class's Expression property . . ."

http://msdn.microsoft.com/en-us/libr...xpression.aspx

dim a = dt.Select("IssuerName LIKE 'B*'")

worked