Uploading a file and checking it

An upload control lets a visitor send a file. Because that file comes from outside, it must be checked before it is trusted.

The control and the save

if (fileUpload.HasFile)
{
    string name = System.IO.Path.GetFileName(fileUpload.FileName);
    string folder = Server.MapPath("~/uploads/");
    fileUpload.SaveAs(System.IO.Path.Combine(folder, name));
    statusLabel.Text = "Stored " + name;
}

What to validate

• The size, so a huge file cannot fill your disk.
• The extension and the real content type, not just the name the browser reported.
• The destination path, so a crafted name cannot escape the folder you intended.

That completes the data control track. Continue to web services and reuse to share the same logic with other applications.