"Issue with PDF Attachments: Unable to Display Data in Gmail Client" CSHARP

Question

I am facing an issue when sending an email with an attachment in C# using the SmtpClient. The email is successfully delivered to Gmail, but when I open the attachment in the Gmail client, there is no data shown.

 using (var stream = file.OpenReadStream())
 {
    var attachment = new Attachment(stream, file.FileName);  
    mailMessage.Attachments.Add(attachment);
    Client.Send(mailMessage);
    attachment.Dispose();  
 }

Checked the generated PDF file independently to ensure data is present. Examined the email content to verify that it includes the expected data. Debugged the C# code to confirm that the attachment is being added to the email correctly. Reviewed Gmail client settings to check if there are any specific requirements for displaying attachments.

Expectation: I expected the Gmail client to display the data in the attachment as intended. However, despite the email being sent successfully, the attachment appears empty when opened in the Gmail client.