Excel interop prevent showing password dialog

10
votes

I am writing a program to clean excel files from empty rows and columns, i started from my own question Fastest method to remove Empty rows and Columns From Excel Files using Interop and everything is going fine.

The problem is that i want to prevent excel from showing the password dialog when the workbook is password protected and to throw an exception instead of that.

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i am using the following code to open excel files using interop:

 m_XlApp = New Excel.Application
 m_XlApp.visible = False
 m_XlApp.DisplayAlerts = False

 Dim m_xlWrkbs As Excel.Workbooks = m_XlApp.Workbooks
 Dim m_xlWrkb As Excel.Workbook
 m_xlWrkb = m_xlWrkbs.Open(strFile)

 m_xlWrkb.DoNotPromptForConvert = true

i tried to pass an empty password as some links suggested

m_xlWrkb = m_xlWrkbs.Open(strFile, Password:="")

Or using 

m_xlWrkb.Unprotect("")

but no luck.

any suggestions?

3
c#excelvb.netwinformsexcel-interop
interop has the HasPassword property msdn.microsoft.com/en-us/library/… Then you can thrown an exception by yourself – Esselans
@Jaxedin i agree with you but this property cannot be accessed before openning the file, so it will not work, the password dialog is shown when workbook.open() method is called – Hadi
@Jaxedin i found a solution take a look – Hadi

3 Answers

8
votes

I found a solution, but i will accept other working answers

Problem

When passing an empty string as password the excel consider it as nothing. So it ask for a password and show the dialog.

Solution

The solution is to pass a single quotation as a password, excel will consider it as empty string. If workbook is not password protected it will open, else it will throw the following exception

The password you supplied is not correct. Verify that the CAPS LOCK key is off and be sure to use the correct capitalization

The code will be:

m_xlWrkb = m_xlWrkbs.Open(strFile, Password:="'")

Note

In microsoft excel, single quotation on the beginning of a value is used to force text formatting.

example; '0 is readed as a text of value 0

3
votes

Do not use Nothing for method arguments you do not want to supply.

Instead of:

m_xlWrkb = m_xlWrkbs.Open(strFile, Nothing, Nothing, Nothing, "", Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing)

use any of the following:

m_xlWrkb = m_xlWrkbs.Open(strFile, Password:="")

or

m_xlWrkb = m_xlWrkbs.Open(strFile, , , , "", , , , , , , , , , )

or

Dim missing As System.Reflection.Missing = System.Reflection.Missing.Value
m_xlWrkb = m_xlWrkbs.Open(strFile,missing, missing, missing, "", missing, missing, missing, missing, missing, missing, missing, missing, missing, missing)

If the Workbook is password protected, doing this will cause a COMException to be thrown with a message of:

"The password you supplied is not correct. Verify that the CAPS LOCK key is off and be sure to use the correct capitalization."

If the Workbook is not password protected, no exception will be thrown assuming the file is accessible.

You can also define the "missing" object shown above like this:

Dim missing As Object = Type.Missing

Type.Missing and System.Reflection.Missing refer to the same object.

2
votes

Concerning your solution, are you sure that it will not work with anything, that is not the password? Something like this:

Public Function wb_get_workbook(ByVal sFullName As String) As Workbook

    Dim sFile As String
    Dim wbReturn As Workbook

    sFile = Dir(sFullName)

    On Error Resume Next
        Set wbReturn = Workbooks(sFile)

        If wbReturn Is Nothing Then
            Application.AskToUpdateLinks = False
            Set wbReturn = Workbooks.Open(sFullName, , , , "ThisIsDefinitelyAPasswordThatNooneHasUsed681")
        End If
    On Error GoTo 0

    Set wb_get_workbook = wbReturn

End Function

Will also throw an error, if it is password protected, and if it is not, then it would not care about the password you are providing. I am trying in VBA, but in C# you use the Excel Application object, so it should not be different.