CLR Function Error 6522 Using System.IO Namespace

I created a clr proc that gets the most recent file within a directory based on the creation time property, see code below. I have attempted to replicate this within a clr scalar valued function in order to assign the resulting value to a variable within SQL server. I am getting the error message:


Msg 6522, Level 16, State 2, Line 1

A .NET Framework error occurred during execution of user-defined routine or aggregate "clr_fn_recentfile":

System.InvalidOperationException: Data access is not allowed in this context. Either the context is a function or method not marked with DataAccessKind.Read or SystemDataAccessKind.Read, is a callback to obtain data from FillRow method of a Table Valued Function, or is a UDT validation method.

System.InvalidOperationException:

at System.Data.SqlServer.Internal.ClrLevelContext.CheckSqlAccessReturnCode(SqlAccessApiReturnCode eRc)

at System.Data.SqlServer.Internal.ClrLevelContext.GetCurrentContext(SmiEventSink sink, Boolean throwIfNotASqlClrThread, Boolean fAllowImpersonation)

at Microsoft.SqlServer.Server.InProcLink.GetCurrentContext(SmiEventSink eventSink)

at Microsoft.SqlServer.Server.SmiContextFactory.GetCurrentContext()

at Microsoft.SqlServer.Server.SqlContext.get_CurrentContext()

at Microsoft.SqlServer.Server.SqlContext.get_Pipe()

at clr_fn_recentfile.clr_fn_recentfile.clr_fn_recentfile(SqlString Filepath)


After trying to troubleshoot this I am aware that this error is rather generic and have not been able to find any specific documenation regardint the use of file system objects with clr functions. I am at a loss. Any help would be appreciated!
STORED PROC CODE WORKS



Code Snippet
Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.IO

Partial Public Class clr_recentfile

_
Public Shared Sub clr_recentfile(ByVal Filepath As SqlString)
Dim strFile As String
Dim sp As SqlPipe = SqlContext.Pipe()
Dim maxDate As Date
Dim fil As String
Dim qry As New SqlCommand()
Try
If Directory.Exists(Filepath.ToString) Then

For Each strFile In Directory.GetFiles(Filepath.ToString)
Path.GetFileName(strFile)
fil = Path.GetFileName(strFile).ToString
Dim fi As New FileInfo(strFile)
If maxDate = Nothing Then
maxDate = fi.CreationTime
fil = fi.FullName.ToString
Else
If maxDate < fi.CreationTime Then
maxDate = fi.CreationTime
End If
End If

Next
Else
sp.Send("Directory does not exist")
Return
End If
If fil <> Nothing Then
qry.CommandText = " SELECT '" & fil & "'"
'Execute the query and pass the result set back to SQL
sp.ExecuteAndSend(qry)
sp.Send(qry.CommandText.ToString)
End If
Catch ex As Exception
sp.Send(ex.Message.ToString)
End Try
End Sub
End Class






FUNCTION CODE DOES NOT WORK WITH ABOVE ERROR



Code Snippet
Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.IO

Partial Public Class clr_fn_recentfile
<Microsoft.SqlServer.Server.SqlFunction()> _
Public Shared Function clr_fn_recentfile(ByVal Filepath As SqlString) As SqlString
Dim strFile As String
Dim sp As SqlPipe = SqlContext.Pipe()
Dim maxDate As Date
Dim fil As String
Dim qry As New SqlCommand()
Try
If Directory.Exists(Filepath.ToString) Then

For Each strFile In Directory.GetFiles(Filepath.ToString)
Path.GetFileName(strFile)
fil = Path.GetFileName(strFile).ToString
Dim fi As New FileInfo(strFile)
If maxDate = Nothing Then
maxDate = fi.CreationTime
fil = fi.FullName.ToString
Else
If maxDate < fi.CreationTime Then
maxDate = fi.CreationTime
End If
End If

Next
Else
sp.Send("Directory does not exist")
Exit Function
End If
If fil <> Nothing Then
Return fil
End If
Catch ex As Exception
sp.Send(ex.Message.ToString)
End Try

End Function
End Class