Problem to ObjectDisposedException

System.ObjectDisposedException was unhandled
  HResult=-2146232798
  Message=Cannot access a disposed object. Object name: 'SpreadsheetDocument'  Source=DocumentFormat.OpenXml
  ObjectName=SpreadsheetDocument
  StackTrace:
       at DocumentFormat.OpenXml.Packaging.OpenXmlPackage.ThrowIfObjectDisposed()
       at DocumentFormat.OpenXml.Packaging.OpenXmlPartContainer.GetSubPartOfType[T]()
       at DocumentFormat.OpenXml.Packaging.SpreadsheetDocument.get_WorkbookPart()
       at WindowsFormsApplication2.Form1.InsertText(SpreadsheetDocument spreadSheet, String SheetName0, String text, String CellRowRef0, UInt32 CellColRef0) in c:\dp13\General Application\WindowsFormsApplication9_4_0_4\WindowsFormsApplication2\Form1.cs:line 659
       at WindowsFormsApplication2.Form1.menuItem5_Click(Object sender, EventArgs e) in c:\dp13\General Application\WindowsFormsApplication9_4_0_4\WindowsFormsApplication2\Form1.cs:line 198
       at System.Windows.Forms.MenuItem.OnClick(EventArgs e)
       at System.Windows.Forms.MenuItem.MenuItemData.Execute()
       at System.Windows.Forms.Command.Invoke()
       at System.Windows.Forms.Command.DispatchID(Int32 id)
       at System.Windows.Forms.Control.WmCommand(Message& m)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
       at System.Windows.Forms.Form.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at WindowsFormsApplication2.Program.Main() in c:\dp13\General Application\WindowsFormsApplication9_4_0_4\WindowsFormsApplication2\Program.cs:line 19
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

            if (spreadSheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().Count() > 0)

        public static void InsertText(SpreadsheetDocument spreadSheet, string SheetName0, string text, string CellRowRef0, uint CellColRef0)
        {
            //using (SpreadsheetDocument spreadSheet = SpreadsheetDocument.Open(docName, true))
            // Open the document for editing.
            //Using(SpreadsheetDocument spreadSheet = SpreadsheetDocument.Open(docName, true))
            //{
            // Get the SharedStringTablePart. If it does not exist, create a new one.
            SharedStringTablePart shareStringPart;
            if (spreadSheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().Count() > 0)
            {
                shareStringPart = spreadSheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().First();
            }
            else
            {
                shareStringPart = spreadSheet.WorkbookPart.AddNewPart<SharedStringTablePart>();
            }

Many Thanks & Best Regards, Hua Min