With the help of the hint and help links posted by
Maciej Los I found a solution for my question. Thank you Maciej Los.
List<bills> lstbills = Context.bills.ToList();
using (SqlBulkCopy sqlbulkCopy = new SqlBulkCopy(mconn, SqlBulkCopyOptions.Default, mtrans))
{
sqlbulkCopy.DestinationTableName = "mast_bills";
sqlbulkCopy.WriteToServer(lstbills.AsDataReaderOfObjects());
}
To get AsDataReaderOfObjects() extension I added
BenGribaudoLLC.IEnumerableHelpers.DataReaderAdapter as a nuget package.