Now we will create a new windows application and add a button control, in click on button click we will verify and remove the password from the excel file. First, we will install the ExcelDataReader NuGet package.
C#.Net
using ExcelDataReader;
using ExcelDataReader.Exceptions;
using System.Runtime.InteropServices;
using System.Text;
namespace WinFormsApp3
{
public partial class VerifyExcelFileEncrypted : Form
{
public VerifyExcelFileEncrypted()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string excelFilePath = "C:\\Personal\\Files\\Test.xlsx";
bool status = ExcelStatus(excelFilePath);
if (status)
{
try
{
// Provide the current password for the workbook
string currentPassword = "123";
// Remove password using Excel COM automation (requires Excel installed)
RemovePasswordWithExcelInterop(excelFilePath, currentPassword);
MessageBox.Show("Password removed (file overwritten).");
}
catch (Exception ex)
{
MessageBox.Show("Failed to remove password: " + ex.Message);
}
}
else
{
MessageBox.Show("The Excel file is not encrypted.");
}
}
private bool ExcelStatus(string filePath)
{
try
{
using (var stream = File.OpenRead(filePath))
{
Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
using (ExcelReaderFactory.CreateReader(stream)) { }
}
}
catch (InvalidPasswordException)
{
return true;
}
return false;
}
/// <summary>
/// Remove password.
/// </summary>
private void RemovePasswordWithExcelInterop(string filePath, string password)
{
if (!File.Exists(filePath))
throw new FileNotFoundException("Excel file not found.", filePath);
Type excelType = Type.GetTypeFromProgID("Excel.Application");
if (excelType == null)
throw new InvalidOperationException("Microsoft Excel is not installed on this machine.");
object excel = null;
object workbook = null;
try
{
excel = Activator.CreateInstance(excelType);
dynamic app = excel;
app.DisplayAlerts = false;
app.Visible = false;
// Open the workbook providing the password
workbook = app.Workbooks.Open(filePath, ReadOnly: false, Password: password);
// Use dynamic to call SaveAs on the workbook
dynamic wb = workbook;
wb.SaveAs(Filename: filePath, Password: "", WriteResPassword: "", ReadOnlyRecommended: false, CreateBackup: false);
wb.Close(SaveChanges: false);
}
finally
{
// Cleanup COM objects
try
{
if (workbook != null)
Marshal.ReleaseComObject(workbook);
}
catch { /* ignore */ }
try
{
if (excel != null)
{
try
{
((dynamic)excel).Quit();
}
catch { /* ignore */ }
Marshal.ReleaseComObject(excel);
}
}
catch { /* ignore */ }
GC.Collect();
GC.WaitForPendingFinalizers();
}
}
}
} VB.Net
Imports ExcelDataReader
Imports ExcelDataReader.Exceptions
Imports System.Runtime.InteropServices
Imports System.Text
Namespace WinFormsApp3
Public Partial Class VerifyExcelFileEncrypted
Inherits Form
Public Sub New()
InitializeComponent()
End Sub
Private Sub button1_Click(sender As Object, e As EventArgs)
Dim excelFilePath = "C:\Personal\Files\Test.xlsx"
Dim status = ExcelStatus(excelFilePath)
If status Then
Try
' Provide the current password for the workbook
Dim currentPassword = "123"
' Remove password using Excel COM automation (requires Excel installed)
RemovePasswordWithExcelInterop(excelFilePath, currentPassword)
MessageBox.Show("Password removed (file overwritten).")
Catch ex As Exception
MessageBox.Show("Failed to remove password: " & ex.Message.ToString())
End Try
Else
MessageBox.Show("The Excel file is not encrypted.")
End If
End Sub
Private Function ExcelStatus(filePath As String) As Boolean
Try
Using stream = File.OpenRead(filePath)
Encoding.RegisterProvider(CodePagesEncodingProvider.Instance)
Using ExcelReaderFactory.CreateReader(stream)
End Using
End Using
Catch __unusedInvalidPasswordException1__ As InvalidPasswordException
Return True
End Try
Return False
End Function
''' <summary>
''' Remove password.
''' </summary>
Private Sub RemovePasswordWithExcelInterop(filePath As String, password As String)
If Not File.Exists(filePath) Then Throw New FileNotFoundException("Excel file not found.", filePath)
Dim excelType = Type.GetTypeFromProgID("Excel.Application")
If excelType Is Nothing Then Throw New InvalidOperationException("Microsoft Excel is not installed on this machine.")
Dim excel As Object = Nothing
Dim workbook As Object = Nothing
Try
excel = Activator.CreateInstance(excelType)
Dim app As dynamic = excel
app.DisplayAlerts = False
app.Visible = False
' Open the workbook providing the password
workbook = app.Workbooks.Open(filePath, [ReadOnly]:=False, Password:=password)
' Use dynamic to call SaveAs on the workbook
Dim wb As dynamic = workbook
wb.SaveAs(Filename:=filePath, Password:="", WriteResPassword:="", ReadOnlyRecommended:=False, CreateBackup:=False)
wb.Close(SaveChanges:=False)
Finally
' Cleanup COM objects
Try
If workbook IsNot Nothing Then Marshal.ReleaseComObject(workbook)
Catch
End Try
Try
If excel IsNot Nothing Then
Try
CType(excel, dynamic).Quit()
Catch
End Try
Marshal.ReleaseComObject(excel)
End If
Catch
End Try
GC.Collect()
GC.WaitForPendingFinalizers()
End Try
End Sub
End Class
End Namespace In above code first I have stored the path of excel file in a variable. Afte that i have created a method to verify that the file is password protected or not. If it is password protected on that a new variable i have defined where I passed the password of the excel file.
Now I have created a separate method named as RemovePasswordWithExcelInterop(excelFilePath, currentPassword);. In this method I have passed excel file and current password of the excel file. Here I have used Excel COM to open the excel with provided password and saved back the excel without password. This code will require Excel to be installed on the machine. Now we have done, lets run the code and check output. First, we will remove password and after that we will again check the file.
Now let's rerun the application and check again for decrypted file. Here we will get message that file is not encrypted.
