File upload/download failing - asp.net

Question

I'm working on a website where I need to have upload/download functionality. Upload works fine, but when I press Download Uploaded File nearly nothing happens.
//Upload
protected void btnUpload_Click(object sender, EventArgs e)
{
string filename = Path.GetFileName(fileUpload1.PostedFile.FileName);
fileUpload1.SaveAs(Server.MapPath("Files/" + filename));
con.Open();
SqlCommand cmd = new SqlCommand("insert into FilesTable(FileName,FilePath) values(#Name,#Path)", con);
cmd.Parameters.AddWithValue("#Name", filename);
cmd.Parameters.AddWithValue("#Path", "Files/" + filename);
cmd.ExecuteNonQuery();
con.Close();
BindGridviewData();
}
//Download
protected void gvDetails_SelectedIndexChanged(object sender, EventArgs e)
{
SqlCommand com = new SqlCommand("select FileName,FilePath from FilesTable where Id=#Id", con);
com.Parameters.AddWithValue("Id", gvDetails.SelectedRow.Cells[1].Text);
SqlDataReader dr = com.ExecuteReader();
if (dr.Read())
{
Response.Clear();
Response.Buffer = true;
Response.ContentType = dr["type"].ToString();
Response.AddHeader("content-disposition", "attachment;filename=" + dr["Name"].ToString());
Response.Charset = "";
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.BinaryWrite((byte[])dr["data"]);
Response.End();
}
}

Answer 1

There are few problems with your code:
Your select query only returns FileName and FilePath but you also try to retrieve type and data from database. You can add an extra column in table to store file type since your code already saves uploaded file in Files folder then you can use dr["type"]
You need to use same file path for downloading as well that you used for saving, either store absolute path or relative path in database:
// Uploading
string filePath = Server.MapPath("Files/" + filename); // Absolute path
or
string filePath = "Files/" + filename; // Relative path
...
cmd.Parameters.AddWithValue("#Path", filePath);
// Downloading
string filePath = dr["FilePath"]; // Absolute path
or
string filePath = Server.MapPath(dr["FilePath"]); // Relative path
If file gets saved in folder instead of database then read its contents as bytes for sending to client using File or FileStream etc:
// ReadAllBytes throws memory exception for large files
byte[] fileData = File.ReadAllBytes(filePath);
The select list contains FileName as column name and not just Name, replace dr["Name"] with dr["FileName"]