bool CheckPassword(
    string password
)

Function CheckPassword(
    password As String
) As Boolean

using (Workbook workbook = new Workbook()) {
    workbook.LoadDocument("WriteProtectedDocument.xlsx");
    RemoveWriteProtection(workbook, "password");
}
// ...

private void RemoveWriteProtection(Workbook workbook, string password) {
    var wpOptions = workbook.DocumentSettings.WriteProtection;
    if (wpOptions.IsPasswordProtected && wpOptions.CheckPassword(password))
        wpOptions.ClearPassword();
    else {
        Console.WriteLine("The file is not write-protected or the specified password is invalid!");
        Console.ReadKey();
    }
}

Using workbook As New Workbook()
    workbook.LoadDocument("WriteProtectedDocument.xlsx")
    RemoveWriteProtection(workbook, "password")
End Using
' ...

Private Sub RemoveWriteProtection(workbook As Workbook, password As String)
    Dim wpOptions As WriteProtectionOptions = workbook.DocumentSettings.WriteProtection
    If wpOptions.IsPasswordProtected AndAlso wpOptions.CheckPassword(password) Then
        wpOptions.ClearPassword()
    Else
        Console.WriteLine("The file is not write-protected or the specified password is invalid!")
        Console.ReadKey()
    End If
End Sub