This seems like it ought to work. In this code, intellisense has underlined "d_row.Field(Of String)" and flagged it with the warning:

'Field' is not a member of 'sites'.

So that means it is not recognizing 'Field' as a LINQ operator, it thinks I am trying to access a field named 'Field'.

What is my error?

The goal is to use LINQ to select a distinct column from a list of objects and place it in a list(of string).
Code:
Public Class sites
    Public Property Name As String
    Public Property Location As String

    Public Sub New(n As String, l As String)
        Name = n
        Location = l
    End Sub
End Class

Module Module1

    Sub Main()

        Dim sitelist As New List(Of sites)

        For Each i As String In {"one", "one", "two", "three"}
            Dim site As sites = New sites(i, "test")
            sitelist.Add(site)
        Next

        Dim siterow As List(Of String) = (From d_row In sitelist.AsEnumerable()
                                          Select d_row.Field(Of String)("Name")
                                          Distinct).ToList
    End Sub

End Module