u can use this code...
protected void lnkfilepath_Click(object sender, EventArgs e) // ur link button
{
string filename = lnkfilepath.Text;
string Filpath = Server.MapPath("~/Attachments/" + filename);
DownLoad(Filpath); }
public void DownLoad(string FName){
string path = FName;
System.IO.FileInfo file = new System.IO.FileInfo(path);
if (file.Exists) {
Response.Clear();
Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name); Response.AddHeader("Content-Length", file.Length.ToString());
Response.ContentType = "application/octet-stream"; // download […]
}