Question

 public ActionResult GetAttachment1(string projectID)
        {

                return File("~/Uploads/Project", "application/pdf", projectID);

        }

this code gives an error……

Answer 1

You need to specify an absolute path to the File method. Use Server.MapPath to convert a relative into an absolute path:

public ActionResult GetAttachment1(string projectID)
{
    string projectPath = Server.MapPath("~/Uploads/Project");
    string file = Path.Combine(projectPath, projectID);
    // at this stage file will look something like this 
    // "c:\inetpub\wwwroot\Uploads\Project\foo.pdf". Make sure that
    // this is a valid PDF file and pass it to the File method

    return File(file, "application/pdf", projectID);
}