microsoft jscript runtime error 'null' is null or not an object javascript

<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0"
width="734" class="style3">
<param name="movie" value="<%=swfFilename %>">
<param name="quality" value="high">
<embed src="<%=swfFilename %>" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="1003" height="850"></embed>
</object>


this is my design code for flash player


public string swfFilename;

i had declare this variable


try
{
if (con1.State == ConnectionState.Closed)
{
con1.Open();
}

SqlCommand cmd = new SqlCommand("select registrationkey from tbl_registration where userId='"+lblusername.Text+"' ", con1);
dr = cmd.ExecuteReader();
dr.Read();
if (dr.HasRows)
{
Random_keys = dr[0].ToString();
dr.Close();

//SqlCommand cmd3 = new SqlCommand("select count(id) from tbl_questionSelection where Random_keys='"+Random_keys+"' ", con1);
//dr = cmd3.ExecuteReader();
//dr.Read();
//if (dr.HasRows)
//{
// a =int.Parse( dr[0].ToString());
// dr.Close();
//}
//else
//{
// dr.Close();
//}

//for (int j = 0; j < a; j++)
//{
// SqlCommand cmd4 = new SqlCommand("select id from tbl_questionSelection where Random_keys='"+Random_keys+"'", con1);
// dr = cmd4.ExecuteReader();
// dr.Read();
// if (dr.HasRows)
// {
// id_no = Convert.ToInt32(dr[0].ToString());
// dr.Close();
// }
// else
// {
// dr.Close();
// }

SqlCommand cmd1 = new SqlCommand("select q_id from tbl_questionSelection where Random_keys='" + Random_keys + "'", con1);
SqlDataAdapter da=new SqlDataAdapter(cmd1);
DataSet ds=new DataSet();
da.Fill(ds);


//dr = cmd1.ExecuteReader();
// dr.Read();
// if (dr.HasRows)
// {
// q_id = int.Parse(dr[0].ToString());
// dr.Close();
// }
// else {
// dr.Close();
// }

// if(ds.Tables[0].Rows.Count!=0)

//for( int j = 0;j