AST for LINQ expression in VB.NET

Hello,
I need to create AST for LINQ expression written in both C# and VB.NET.
C# code. I tested following code:

class Program
{
static void Main(string[] args)
{
var q = from c in new Query<Company>() select c;
}
}

AST for this code comes out like this (negative offsets for the code in document.HeaderText). As you can see, it is parsed correctly.

[-227-122] CompilationUnit
[-227-122] ClassDeclaration: Program
[-221--214] QualifiedIdentifier: Program
[-130-82] MethodDeclaration: Name=Main
[-118--114] QualifiedIdentifier: Main
[-123--119] TypeReference: System.Void
[-113--100] ParameterDeclaration
[-113--107] TypeReference: System.String[]
[-8-42] LocalVariableDeclaration
[-4-39] VariableDeclarator
[0-39] TypeReference: System.Object
[-4--3] QualifiedIdentifier: q
[0-39] QueryExpression
[0-30] FromQueryOperator
[5-30] CollectionRangeVariableDeclaration
[5-6] VariableDeclarator
[5-5] TypeReference: _Anonymous
[5-6] QualifiedIdentifier: c
[10-30] ObjectCreationExpression
[14-19] TypeReference: Query`1
[20-27] TypeReference: Company
[31-39] SelectQueryOperator
[38-38] VariableDeclarator
[38-38] TypeReference: _Anonymous
[38-39] SimpleName: c

When I parse an equivalent code in VB.NET:

Imports System.Collections
Imports System.Linq
Module Module1
Public Class TestClass
Sub TestSub()
Dim q = From c In New Query(Of Company) Select c
End Sub
End Class
End Module

the resulting AST does not have any LINQ-related nodes in it:

[-297-187] CompilationUnit
[-297--212] UsingDirectiveSection
[-297--271] UsingDirective
[-289--271] QualifiedIdentifier: System.Collections
[-231--212] UsingDirective
[-223--212] QualifiedIdentifier: System.Linq
[-170-187] StandardModuleDeclaration: Module1
[-163--156] QualifiedIdentifier: Module1
[-115-137] ClassDeclaration: Module1+TestClass
[-102--93] QualifiedIdentifier: TestClass
[-53-88] MethodDeclaration: Name=TestSub
[-49--42] QualifiedIdentifier: TestSub
[0-43] BlockStatement

How can I get correct AST for VB.NET code? Any suggestions are appreciated.