GetRows Method works in VB but not in C#

Can someone look at my code below and tell me what I'm doing wrong I converted VBScript to C# for ASP to ASP.NET migration. (I wasn't able to successfully convert legacy ADO to ADO.NET, so sticking with this) I'm getting an error at this line:

cartValues = RS.GetRows(-1, null, null);

Error Message:

Exception Details: System.Runtime.InteropServices.COMException: Application uses a value of the wrong type for the current operation.

C# Code:

ADODB.ConnectionClass con;
object[] arrVals;
string sqlStr;
ADODB.Recordset RS;
object cartValues;
int i = 0;

con = new ADODB.ConnectionClass();
con.Open("Provider=SQLOLEDB;Data Source=xxx.xxx.xxx.xxx; Network Library=DBMSSOCN; Initial Catalog=xxx;User ID=xxx;Password=xxx;", "", "", -1);

arrVals = Request.QueryString["chkBox"].Split(',');
sqlStr = "SELECT PublicationsID, title, url, price, MaxOrder, qty, govtpubnumber, image, TitleDisplay, CategoryID FROM Publications WHERE ";
for (i = 0; i <= arrVals.GetUpperBound(0); i++)
{
if (i == 0)
sqlStr = sqlStr + "PublicationsID = " + arrVals;
else
{
sqlStr = sqlStr + " OR PublicationsID = " + arrVals;
}
}
sqlStr = sqlStr + " ORDER BY CategoryID, title ";
//Response.Write(sqlStr);

Object RecordsAffected = null;
RS = con.Execute(sqlStr, out RecordsAffected, -1);
cartValues = RS.GetRows(-1, null, null);
Session.Add("cart", cartValues);
RS = null;
con.Close();

I tried converting the original code from VBScript to VB.NET first and it worked fine with no arguments in the GetRows method: cartValues = RS.GetRows(). I found that this method has three arguments and they are all optional in VB but not in C#:

arrayName = Recordset.GetRows(int Rows, object Start, object Fields )

In VB when no arguments are specified, it returns all rows starting from the current row. I need to get the behavior in C#, but I'm not sure what to put in to the second and third arguments. Please help anyone.