LINQ statement to find duplicates. Proper Syntax when: Option Strict On

I am performing a LINQ query to find duplicates in a DataTable.  It is working perfectly with Option Strict OFF.  However, for compliance purposes, I must have Option Strict ON.  Example-A is the original code.  In Example-B, I modified the syntax to get it to compile, but it fails at runtime.

Dim dtDivision4_Results As DataTable
<Fill DataTable>


Example-A: LINQ query when: Option Strict OFF

This code runs properly and returns duplicates in dtDupAccounts

 Dim dtDupAccounts = dtDivision4_Results.AsEnumerable().GroupBy(Function(i) i.Field(Of String)("AccountNumber")).Where(Function(g)
 g.Count() > 1).Select(Function(g) g.Key)


Example-B: LINQ query when: Option Strict ON

The code compiles, but at runtime, I get an "Invalid Cast Exception".

 Dim dtDupAccounts As DataTable = CType(dtDivision4_Results.AsEnumerable().GroupBy(Function(i) i.Field(Of String)
 ("AccountNumber")).Where(Function(g) g.Count() > 1).Select(Function(g) g.Key), DataTable)


The exact exception I get is:

+            $exception      {"Unable to cast object of type 'WhereSelectEnumerableIterator`2[System.Linq.IGrouping`2[System.String,System.Data.DataRow],System.String]' to type 'System.Data.DataTable'."}      System.InvalidCastException


Please help me perfect the syntax of the query in Example-B.
I am a novice to VB.Net and your help in correcting my syntax would be greatly appreciated.