I need help converting this C# Linq query to VB.net. I dont really understand the certain aspects

I am converting an MVC C# application to VB.

I'm running across problem converting Linq.
I've got to do a number of these, so prefer a nice explanation.
When I convert to VB I seem to get null int error which I'm not getting in the C# version.

System.NotSupportedException: 'Unable to cast the type 'System.Nullable`1[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' to type 'System.Object'. LINQ to Entities only supports casting EDM primitive or enumeration types.'

I've tried online converter but they are not giving valid answers.

C#

public List<notesselect> getNotes(int? catid, int? userid, int page = 1, int size = 10)
{
    // pagination stuff
    int startindex = 1;
    startindex = ((page - 1) * size);
    //get all noted which is created by user or shared to user
    var notes = (from c in db.Notes
                 join Category in db.Categorys on c.CategoryId equals Category.CategoryId
                 join d in db.Users on c.CreatedBy equals d.UserId
                 join p in db.NotesAuth on new { NotesId = c.NotesId, isactive = true } equals new { NotesId = p.NotesId, isactive = p.IsActive } into ps
                 from p in ps.DefaultIfEmpty()
                 where c.IsActive == true
                 && (c.CreatedBy == userid || p.UserId == userid)
                 && (catid != null ? c.CategoryId == catid : true)
                 select new notesselect
                 {
                     CategoryId = c.CategoryId,
                     CategoryName = Category.Category,
                     title = c.Title,
                     createby = d.FirstName + " " + d.LastName,
                     noteid = c.NotesId,
                     createdate = c.ChangeDate,
                     lastModifiedOn = c.ChangeDate.ToString()
                 }).OrderByDescending(x => x.createdate);
    if (page > 0)
    {
        return notes.Skip(startindex).Take(size).ToList();
    }
    else
    {
        return notes.ToList();
    }
}

/// <summary>
/// Get Total Count of Notes 
/// </summary>
/// <param name="catid">Category Id</param>
/// <param name="userid">User Id</param>
/// <returns></returns>
public int getNoteCount(int? catid, int? userid)
{
    var total = (from c in db.Notes
                 join Category in db.Categorys on c.CategoryId equals Category.CategoryId
                 join d in db.Users on c.CreatedBy equals d.UserId
                 join p in db.NotesAuth on new { NotesId = c.NotesId, isactive = true } equals new { NotesId = p.NotesId, isactive = p.IsActive } into ps
                 from p in ps.DefaultIfEmpty()
                 where c.IsActive == true
                 && (c.CreatedBy == userid || p.UserId == userid)
                  && (catid != null ? c.CategoryId == catid : true)
                 select c).Count();
    return total;
}

Vb Converted code

Public Function getNotes(ByVal catid? As Integer, ByVal userid? As Integer, Optional ByVal page As Integer = 1, Optional ByVal size As Integer = 10) As List(Of notesselect)
    ' pagination stuff
    Dim startindex As Integer = 1
    startindex = 1 '((page - 1) * size)
    'get all noted which is created by user or shared to user
    Dim notes = (From c In db.Notes
                 Join Category In db.Categorys On CType(c.CategoryId, Integer?) Equals CType(Category.CategoryId, Integer?)
                 Join d In db.Users On c.CreatedBy Equals CType(d.UserId, Integer?)
                 Group Join p In db.NotesAuth On New With {
          .NotesId = c.NotesId,
          .isactive = True
        } Equals New With {
          .NotesId = p.NotesId,
         .isactive = p.IsActive
        } Into ps = Group
                 From p In ps.DefaultIfEmpty()
                 Where c.IsActive = True AndAlso (userid.Equals(c.CreatedBy) OrElse userid.Equals(p.UserId)) AndAlso (If(catid IsNot Nothing, catid.Equals(c.CategoryId), True))
                 Select New notesselect With {
            .CategoryId = c.CategoryId,
            .CategoryName = Category.Category,
            .title = c.Title,
            .createby = d.FirstName & " " & d.LastName,
            .noteid = c.NotesId,
            .createdate = c.ChangeDate,
            .lastModifiedOn = CStr(c.ChangeDate.ToString)
        }).OrderByDescending(Function(x) x.createdate)
    If page > 0 Then
        Return notes.Skip(startindex).Take(size).ToList()
    Else
        Return notes.ToList()
    End If
    'Dim InvoiceNo = If(dbContext.table.where(Function(x) DirectCast(x.ICOD, System.Nullable(Of Integer))), "NCOD")
End Function

''' <summary>
''' Get Total Count of Notes 
''' </summary>
''' <param name="catid">Category Id</param>
''' <param name="userid">User Id</param>
''' <returns></returns>
Public Function getNoteCount(ByVal catid? As Integer, ByVal userid? As Integer) As Integer
    Dim total = (
        From c In db.Notes
        Join Category In db.Categorys On CType(c.CategoryId, Integer?) Equals Category.CategoryId
        Join d In db.Users On CType(c.CreatedBy, Integer?) Equals CType(d.UserId, Integer?)
        Group Join p In db.NotesAuth On New With {
            Key .NotesId = c.NotesId,
            Key .isactive = True
        } Equals New With {
            Key .NotesId = p.NotesId,
            Key .isactive = p.IsActive
        } Into ps = Group
        From p In ps.DefaultIfEmpty()
        Where c.IsActive = True AndAlso (userid.Equals(c.CreatedBy) OrElse userid.Equals(p.UserId)) AndAlso (If(catid IsNot Nothing, catid.Equals(c.CategoryId), True))
        Select c).Count()
    Return total
End Function