User applicationExcel.Quit()；应用程序退出不了

If calling `applicationExcel.Quit()` doesn't seem to close the Excel application, there are a few additional steps you can take to troubleshoot and ensure that Excel is properly closed:

1. **Release COM objects:** Make sure you release all COM objects associated with Excel. This includes workbooks, worksheets, and other objects. Failing to release these objects can prevent Excel from closing.

    ```csharp
    // Assuming 'workbook' is an instance of Excel.Workbook
    workbook.Close(false);
    System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
    ```

2. **Close all workbooks:** Before quitting Excel, make sure you close all open workbooks.

    ```csharp
    foreach (Excel.Workbook workbook in applicationExcel.Workbooks)
    {
        workbook.Close(false);
        System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
    }
    ```

3. **Release the Excel Application object:** After closing all workbooks, release the Excel application object.

    ```csharp
    applicationExcel.Quit();
    System.Runtime.InteropServices.Marshal.ReleaseComObject(applicationExcel);
    ```

4. **Force Excel process termination:** If all else fails, you can forcefully terminate the Excel process. However, use this approach with caution, as it may result in data loss if there are unsaved changes.

    ```csharp
    System.Diagnostics.Process[] excelProcesses = System.Diagnostics.Process.GetProcessesByName("Excel");
    
    foreach (System.Diagnostics.Process process in excelProcesses)
    {
        process.Kill();
    }
    ```

   Note: Forcibly terminating the Excel process should be a last resort and should be used cautiously, especially in production code.

Make sure you follow these steps in the correct order. Additionally, make sure your application is properly releasing COM objects throughout its lifetime to prevent memory leaks.

Remember to test thoroughly and consider the impact on user experience, especially when forcefully terminating processes. If possible, find and fix the root cause of the issue rather than relying on process termination.