C# how to close excel application in Excel VSTO AddIn - excel

Question

I have created an Excel VSTO Addin which will show a message box with yes, no and cancel as button options on the close event of Current document.
I have opened 2 excel documents to edit. After I complete my edit I try to close one of them, when I click on document close button my message box will appear.
If I click on "No" then all the changes should be discarded and the document should be closed. Other documents should not be closed.
This is the code I used on Don't save action
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
this.Application.WorkbookBeforeClose += Application_WorkbookBeforeClose;
}
private void Application_WorkbookBeforeClose(Excel.Workbook Wb, ref bool Cancel)
{
DialogResult result = MessageBox.Show("Do you want to save changes to " + Wb.Name + "?", "Microsoft Excel ", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button1);
switch (result)
{
case DialogResult.Yes:
Wb.Save();
break;
case DialogResult.No:
int count = this.Application.Workbooks.Count;
if(count > 0)
{
if (count == 1)
{
Excel.Application excel =Globals.ThisAddIn.Application;
Workbooks workbooks = excel.Workbooks;
foreach (Workbook wb in workbooks)
{
wb.Close(false, missing, missing);
}
workbooks = null;
excel.Quit();
excel = null;
}
else
{
Wb.Close(false, missing, missing);
}
}
break;
case DialogResult.Cancel:
Cancel = true;
break;
}
}
If morethan one excel document is opened for edit, then Excel vsto addin should close the particular excel docuemnent in which the close actions is performed and other documents should remain opened. My method closes the document but not closing the application.
How to close the Excel Application completely? my excel appear like this

Answer 1

The following code works for me, but it's important to keep in mind that the add-in technology wasn't really created with quitting the host application from within the add-in. So, "your mileage may vary".
Unlike the code in the question, this does not use Marshal.ReleaseComObject. This method is a "last resort" and forces an immediate release of the object. Once an object has been force-released the code can no longer work with it - but VSTO needs to do its internal clean-up. The method should only be used if the standard methods of releasing COM objects aren't doing the job. VSTO, in any case, as part of its "service" to the developer, takes care of standard releasing of COM objects properly declared and instantiated in the project. So it's enough, really, to set objects to null when they're no longer needed, which releases them for standard garbage collection. When VSTO goes out-of-process the objects will be released at the COM level, at the very latest.
private void btnQuitExcel_Click(object sender, RibbonControlEventArgs e)
{
Excel.Application xlApp = Globals.ThisAddIn.Application;
Excel.Workbooks wbs = xlApp.Workbooks;
int nrWbs = wbs.Count;
if (nrWbs > 0)
{
foreach (Excel.Workbook wb in wbs)
{
wb.Close(false, missing, missing);
}
}
wbs = null;
xlApp.Quit();
xlApp = null;
}

Answer 2

Already answered on Stack Overflow, see if it helps you
As outlined above, quitting Excel requires invoking the Quit method from within VBA code.