I have designed a .net application which will open an Excel file at the time of login and use it to print a report. It will be closed while logging out the user. I set visible to false for Excel file, so that user doesn't know about the background process.
But if anybody opens any other Excel file during this time, my report Excel file becomes visible and the Excel object is collapsed. I have to go to task manager and kill the all open Excel instances to fix this.
Code:
Private Sub OK_Click(sender As Object, e As EventArgs) Handles OK.Click
Try
Dim dt As New DataTable()
Dim Adapter As New SqlDataAdapter()
ConnectMe()
Dim SQLCmd As New SqlCommand("uspLogin", Con)
SQLCmd.CommandType = CommandType.StoredProcedure
SQLCmd.Parameters.AddWithValue("@pLoginName", UsernameTextBox.Text.Trim())
SQLCmd.Parameters.AddWithValue("@pPassword", PasswordTextBox.Text.Trim())
Adapter.SelectCommand = SQLCmd
Adapter.Fill(dt)
SQLCmd.Dispose()
If dt.Rows.Count > 0 Then
Me.Cursor = Cursors.WaitCursor
Loading.Show()
OpenAllTempaltes()
Me.Hide()
Con.Close()
Me.Cursor = Cursors.Arrow
Else
MsgBox("Your Credential is Wrong !!!", MsgBoxStyle.OkOnly + MsgBoxStyle.Critical, "Login")
UsernameTextBox.Text = ""
PasswordTextBox.Text = ""
UsernameTextBox.Focus()
End If
Catch ex As Exception
Application.Exit()
End Try
End Sub
Public Sub OpenAllTempaltes()
Try
xlWorkBook = xlApp.Workbooks.Open(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "Templates", "Excel_Templates_GST.xlsm"), Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, True)
Catch ex As Exception
Throw
End Try
End Sub
Public Sub CloseAllTempaltes()
Try
CleanUp(xlApp, xlWorkBook, xlWorkSheet)
Catch ex As Exception
ExceptionLog("PrintPage", "CloseAllTempaltes", ex.ToString(), DateTime.Now.ToString("dd-MMM-yyyy"))
Finally
GC.Collect()
End Try
End Sub
How can I prevent this?
One of the causes of Excel won’t open Windows 10 is that your Excel is set to ignore other applications that use DDE. The function of the DDE is to send a message to Excel once you double-click a file. Thus, Excel instructs to open the file.
In File 1 shrink the window so you can see both the excel file and your list of other excel files. In file 1 double click any cell so that you see the cursor blinking in the cell waiting for input. Now double click on another excel file to try and open it.
But when I run it with "C:\" and "scratch.xlsx", the Open () call throws the following error: Microsoft Excel cannot access the file 'C:\scratch.xlsx'. There are several possible reasons: • The file name or path does not exist.
When you double-click a Microsoft Excel file type (.xls), Excel starts as expected, but then you may receive an error message that is similar to the following: C:\ filename .xls' could not be found. Check the spelling of the file name, and verify that the file location is correct.
Use the IgnoreRemoteRequests
property of the Excel application object:
xlApp.IgnoreRemoteRequests = True
This is the equivalent of checking the Excel UI option at
File | Options | Advanced | General | Ignore other applications that use Dynamic Data Exchange (DDE).
(See this related answer on SuperUser.)
I couldn't conveniently reproduce your scenario with a .NET application, but ran some tests by late binding an Excel.Application object from Word VBA and it worked as intended. I created a hidden Excel application, and was able to perform actions on it before and after opening files by double-clicking in File Explorer.
In my tests, the setting was not still toggled on the next time I opened Excel normally, but you might want to capture its value and restore it before quitting your application object, in case that behavior isn't universal.
Edit: This behavior has been around since at least Excel 2003, and I verified using Excel 2016 (32-bit).
In Excel 2013 or later, Excel switched to a single document interface: each workbook opens in its own window.
At least through 2016, the Visual Basic Editor has remained a multiple document interface, and you can easily see which files are open in an application session by looking at the Project Explorer pane in the VBE.
Looks like your problem is caused by the same instance of xlApp. What I would do is simple: I would initialize new instance of xlApp and then quite that instance of the application. This way it won't interfere with any other open instance of Excel. Here is how I use it in C#:
using Excel = Microsoft.Office.Interop.Excel;
Excel.Application xlApp = new Excel.Application(); // by default this is invisible
do whatever you have to do with the new instance of xlApp and then quite the application. Once you quite the application it won't be in your task manager.
xlApp.Application.Quit();
I have designed several applications where I had to process the same Excel files that most likely would've been open by those same users. This approach (opening new instance of excel in invisible mode and then quitting the application) never caused any problems for me.
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