Server Error in '/' Application.

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
Source Error:
Line 217: if (ds != null)
Line 218: {
Line 219: ds.Clear();
Line 220: ds.Tables.Clear();
Line 221: ds.Dispose();
Source File: e:\web\localuser\asp\seekdatasheet.com\App_Code\Netfs.cs Line: 219
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
System.Data.DataSet.Clear() +102
Netfs.NetSys.ReturnTable(String RunSqlString) in e:\web\localuser\asp\seekdatasheet.com\App_Code\Netfs.cs:219
_Default.Page_Load(Object sender, EventArgs e) in e:\web\localuser\asp\seekdatasheet.com\Default.aspx.cs:24
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627
Version Information: Microsoft .NET Framework Version:2.0.50727.3643; ASP.NET Version:2.0.50727.3634