adding data two times

[Selen]

Hello,
I add my data to dropdownlist on load .My data count is 3 But the first page
load my data comes 6 .The others it comes 3. My code is

SqlConnection conn=new SqlConnection ();

conn.ConnectionString
="server=(local)\\sql2000;database=db_Kalite_Data;uid=sa;pwd=antalya";

conn.Open ();


string strCommand="select EqpNo from tb_Equipment";

DataSet ds=new DataSet ();

SqlDataAdapter da=new SqlDataAdapter (strCommand,conn);

da.Fill(ds,"tb_Equipment");


this.drpEqpNo .DataSource =ds.Tables ["tb_Equipment"].DefaultView ;

this.drpEqpNo .DataTextField ="EqpNo";

this.drpEqpNo .DataBind ();

this.DataBind();

Thanks