How to detect if a Word document is password protected before uploading the file to server?

Question

I am working on a website, which allows users to upload different file formats. We need to restrict the user from uploading password protected files.

Is there a way

Answer 1

The Following Is In The .aspx Source File

 Page Language="C#" AutoEventWireup="true" CodeBehind="TestForm.aspx.cs" Inherits="TestApp.TestForm"

 !DOCTYPE html PUBLIC
 Reference Page ="~/TestForm.aspx" // Note: Removed all HTML tags

    protected void Upload_Click(object sender, EventArgs e)
    {
        String noPW = "C:\\Users\\David\\Desktop\\Doc1.docx";
        String pwProtected = "C:\\Users\\David\\Desktop\\Test.docx"; 
    //         if (isProtected(pwProtected))
    //             outcome.Text = ("Document Is Password Protected");
    //         else
    //             outcome.Text = ("Document Is NOT Password Protected");

        if (isProtected(noPW))
            outcome.Text = ("Document Is Password Protected");
        else
            outcome.Text = ("Document Is NOT Password Protected");
    }

The Following Is In The .aspx.cs Code Behind File

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using Microsoft.Office.Interop.Word;
    using System.Runtime.InteropServices;
    using Microsoft.Office.Interop.Word;


    namespace TestApp
    {
        public partial class TestForm : System.Web.UI.Page
        {

            protected void Page_Load(object sender, EventArgs e)
            {

            }
            public static bool isProtected(object filePath)
            {
                Application myapp = new Application();

                object pw = "thispassword";
                try
                {

                    // Trying this for Word document
                    myapp.Documents.Open(ref filePath, PasswordDocument: ref pw); // try open
                    myapp.Documents[ref filePath].Close();  // close it if it does open    
                }
                catch (COMException ex)
                {
                    if (ex.HResult == -2146822880) // Can't Open Doc Caused By Invalid Password
                        return true;
                    else
                        Console.WriteLine(ex.Message + "  " + ex.HResult);  // For debugging, have only tested this one document.
                }
                return false;
            }
        }

    }

At least on my computer, I get the expected output for both files, but this is not exactly what you call an exhaustive test of the code. In addition, I tried to upload a file using a FileUpload Control, and I got the COM error "Cannot Find C:\Windows\System\fileName.docx" which confused me just because the the file uploaded came from my desktop, but you probably know why that occurs as you are more familiar with ASP.NET than I am. Either way, this code is just something to try, hope that helps.