pdf using database

i have about 500 pdf in my website to be displayed....as i am using iframe ,but i ddnt filter the same pdf as i have stored the pdf name iin database....i retrive name from database but couldnt retrive the pdf.//i am posting my code....help///

string query = "SELECT distinct(pdfname) FROM feeder where div='" + DropDownList2.Text + "' and grid='" + DropDownList3.Text + "' and feeder='" + DropDownList4.Text + "' ";

DataTable dt1 = new DataTable();

dt1 = cs.display(query);

if (dt1.Rows.Count > 0)

{

string pdf1 = dt1.Rows[0]["pdfname"].ToString();

// Iframe1.Attributes.Add("src", "pdf/"+dt1.Rows[0]["pdfname"].ToString());

//string szPdfPath = Server.Mappath("D:\\test.pdf");

string pdf2=Server.MapPath("pdf/"+pdf1);

//Iframe1.Attributes.Add("src", "pdf/" + pdf1);

Iframe1.Attributes.Add("src",pdf2);

}

help needed...