Issue in save and retreive file in postgres

Greetings,

I am a software programmer and working on a .net web
application(ASP.NET4.0, c# ).
I am new to postgres and for my current project I am using postgres as
database.

In this need functionality to upload a pdf file to database and then
retrieve it again from database.
I have taken bytea column in my table to store binary file data. I am
taking byte array to convert the data.

When I try to retrieve this pdf file from database ,its not working.
Please see the below code and suggest me some solution.

Here is my code:
3. ########## Database table ############

CREATE TABLE testimage
(
id integer,
img bytea
)

2. ########## function to save file in database
protected int UploadDocumentsPostgres()
{
int result = 0;
if (fuDocuments.HasFile)
{
fuDocuments.SaveAs(Server.MapPath("Temp/") +
fuDocuments.FileName);

using (FileStream pgFileStream = new
FileStream(Server.MapPath("Temp/" + fuDocuments.FileName), FileMode.Open,
FileAccess.Read))
{
using (BinaryReader pgReader = new BinaryReader(new
BufferedStream(pgFileStream)))
{
byte[] pgByteA =
pgReader.ReadBytes(Convert.ToInt32(pgFileStream.Length));

NpgsqlConnection cn = new
NpgsqlConnection("server=195.100.1.100;port=5433;database=DTMS;user
id=postgres;password=admin(at)123");

NpgsqlCommand cmd = new NpgsqlCommand();
cmd.Connection = cn;
cn.Open();
string sql = "insert into testimage values(@id,@data)";

cmd.Parameters.Add("@id",
NpgsqlTypes.NpgsqlDbType.Integer, 1).Value = 1;
cmd.Parameters.Add("@data",
NpgsqlTypes.NpgsqlDbType.Bytea, pgByteA.Length).Value = pgByteA;

cmd.CommandText = sql;
cmd.ExecuteNonQuery();
cn.Close();

}
}
}
return result;
}

3. ################### Retrieve file from database and save in temp
folder ########################
DataTable dt = new DataTable();
NpgsqlConnection cn = new
NpgsqlConnection("server=195.100.1.100;port=5433;database=DTMS;user
id=postgres;password=admin(at)123");
NpgsqlDataAdapter sda = new NpgsqlDataAdapter("select * from
testimage", cn);
sda.Fill(dt);

if (dt.Rows.Count > 0)
{
byte[] doc = (byte[])(dt.Rows[0]["img"]);
FileStream fs = new
System.IO.FileStream(Server.MapPath("Temp/") + "temp.PDF", FileMode.Create,
FileAccess.Write);
BinaryWriter bw = new BinaryWriter(new BufferedStream(fs));

bw.Write(doc, 0, doc.Length);
bw.Flush();
bw.Close();
fs.Close();
}
--
*Thanks & Regards
Vishwas Dwivedi
Contact No: +91-9460968854*