I am new to C# and Windows Forms.

I am using syncfusion C# library to encrypt / decrypt Word files.

I am using Async / Await tasks to decrypt files in bulk.

I have no problem to encrypt / decrypt one file or to encrypt multiple files.

I encountered the problem when trying to decrypt multiple word files or in bulk.

When decrypting one file with a wrong password, I get an exception and everything works fine.

But during bulk files decryption using await Task.WhenAll(tasks) inside try-catch block, I am not getting any exception while from the first task (first file to decrypt) I should get an exception because the password is wrong.

During entire week I tried most of the provided solutions everywhere but not successful and I don’t know what I have to do.

Thank you very much!

The code should throw an exception when the first task is not successful but it’s not.

GetPathOrExtention gte = new GetPathOrExtention();

private void DecryptDOCXFiles(string fileName)
{
    FileStream inputStream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
    WordDocument document = new WordDocument(inputStream, FormatType.Docx, TbDecPwd1.Text);

    FileStream outputStream = new FileStream(gte.GetDirPath(fileName) + "\" + gte.GetfileName(fileName).Replace("Encrypted-", ""), FileMode.Create, FileAccess.Write);
    document.Save(outputStream, FormatType.Docx);
    inputStream.Close();
    outputStream.Close();
}

private async Task DecryptWordFiles()
{
    OpenFileDialog ofd = new OpenFileDialog();
    ofd.Filter = "docx files (*.docx)|*.docx|All files (*.*)|*.*";
    ofd.Multiselect = true;
    var tasks = new List<Task>();

    if (TbDecPwd1.Text != "" && ofd.ShowDialog() == DialogResult.OK)
    {
        foreach (string file in ofd.FileNames)
        {
            if (gte.GetFileExtension(file) != ".docx")
            {
                LblProceeding.ResetText();
                MessageBox.Show("Files version is not supported!" + 'n' + 'n' + "Only Word version 2019 and above are supported!", "P-GEN", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            if (gte.GetFileExtension(file) == ".docx")
            {
                LblProceeding.Text = "Proceeding... Do not exit the software!";
                var task = Task.Run(() => DecryptDOCXFiles(file)).ContinueWith(p => progressBar1.PerformStep());
                tasks.Add(task);
            }
        }
    }
    try
        {
            await Task.WhenAll(tasks);  
            LblProceeding.Text = "Done!";
            MessageBox.Show("Files Successfully Decrypted!", "P-GEN", MessageBoxButtons.OK, MessageBoxIcon.Information);
            LblProceeding.ResetText();
            progressBar1.Visible = false;     
        }

    catch (AggregateException)
    {
        LblProceeding.ResetText();
        MessageBox.Show("Ensure the password is correct!" + 'n' + 'n' + "Ensure the files you want to encrypt are not opened in another software!", "P-GEN", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return;
    }

    catch (Exception)
    {
        LblProceeding.ResetText();
        MessageBox.Show("Ensure the password is correct!" + 'n' + 'n' + "Ensure the files you want to encrypt are not opened in another software!", "P-GEN", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return;
    }           
}

private void BtnWordFilesDec_Click(object sender, EventArgs e)
{
    _ = DecryptWordFiles();
}