WCF / ASMX :: Return Dynamic / When Returns To Aspx Error At Aspx(no Exception Gets Caught At  @ Service)?

In our project WCF service is acting as our BLL.

i had scenario where i had to fill list of object class without knowing its type see code:

Added contract

[OperationContract]
dynamic GetReferenceTableData(string tableName);

method in service:

public dynamic GetReferenceTableData(string tableName)
{
try
{
dynamic tableData = ReferenceTableDAL.GetReferenceTableData(tableName);
return tableData;
}
catch (Exception ex)
{
throw;
}
}
method at DAL(ReferenceTableDAL):
public static dynamic GetReferenceTableData(string tableName)
{
Database db = DatabaseFactory.CreateDatabase(Flags.ConnectionStringKey);
DbCommand dbCommand = db.GetStoredProcCommand("USP_GETTABLEDATA");
dynamic objDynamic = null;
if (tableName.ToLower() == "a")
{
objDynamic = new List<A>();
}
else if (tableName.ToLower() == "b")
{
objDynamic = new List<B>();
}
else if (tableName.ToLower() == "c")
{
objDynamic = new List<C>();
}
try
{
db.DiscoverParameters(dbCommand);
dbCommand.Parameters["IN_TABLENAME"].Value = tableName;
DataSet dsTableData = db.ExecuteDataSet(dbCommand);
if (tableName.ToLower() == "a")
{
foreach (DataRow dataRow in dsTableData.Tables[0].Rows)
{
objDynamic.Add((A)dataRow);
}
}
else if (tableName.ToLower() == "b")
{
foreach (DataRow dataRow in dsTableData.Tables[0].Rows)
{
objDynamic.Add((B)dataRow);
}
}
else if (tableName.ToLower() == "c")
{
foreach (DataRow dataRow in dsTableData.Tables[0].Rows)
{
objDynamic.Add((C)dataRow);
}
}
}
catch (Exception ex)
{
throw;
}
return objDynamic;
}
@ Aspx
try
{
using (DataServiceRef.DataServiceClient petService = new DataServiceRef.DataServiceClient())
{
dynamic tableData = petService.GetReferenceTableData(tableName);
//tableData is null ,exception
}
}
catch (Exception ex)
{
throw;
}

There is no exception at dal or service end when i debug list gets filled ok but when returns to aspx error at aspx(no exception gets caught at @ service) but exception at aspx i.e:

Message:The underlying connection was closed: The connection was closed unexpectedly.
Stack Trace: at System.Net.HttpWebRequest.GetResponse()
at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)