if (IsPostBack && DDLCount > 0)
    {
        CreateDropDownLists();
    }
}
public int DDLCount
{
    get
    {
        object temp = ViewState["DDLCount"];
        return temp == null ? 0 : (int)temp;
    }
    set
    {
        ViewState["DDLCount"] = value;
    }
}
private void CreateDropDownLists()
{
    if (DDLCount == 0)
        DDLCount = Convert.ToInt32(TextBox4.Text);
    for (int i = 0; i < DDLCount; i++)
    {
        DropDownList ddl = new DropDownList();


        ddl.ID = "Text" + i;

        LiteralControl l1 = new LiteralControl("<br></br>");

        SqlConnection con1 = new SqlConnection("Data Source=ABC-0D30299B90A;Initial Catalog=JAPIT;Integrated Security=True");
        con1.Open();
        string st = "select  * from   vassign";  //here   we   have    use     where   cause   minum   number   user   dynamic  control 
        SqlCommand cmd = new SqlCommand(st, con1);
        SqlDataReader dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            ddl.Items.Add(dr.GetString(0).ToString());


        }
        con1.Close();



        Panel4.Controls.Add(ddl);
                Panel4.Controls.Add(l1);

    }
}

protected void Button2_Click(object sender, EventArgs e)
{


   SqlConnection con1 = new SqlConnection("Data Source=ABC-0D30299B90A;Initial Catalog=JAPIT;Integrated Security=True");

    con1.Open();

    SqlCommand cmd1= new SqlCommand("insert into assign values('" + DropDownList1.SelectedValue.ToString() + "','" + DropDownList2.SelectedValue.ToString() + "','" + TextBox7.Text + "','" + TextBox2.Text + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + TextBox6.Text + "')", con1);
    cmd1.ExecuteNonQuery();


    con1.Close();

    SqlConnection con2 = new SqlConnection("Data Source=ABC-0D30299B90A;Initial Catalog=JAPIT;Integrated Security=True");
    con2.Open();

    string  str2 = "select   assign_id  from  assign where l_no='" + DropDownList2.SelectedValue + "'";
    SqlCommand cmd2= new SqlCommand(str2, con2);
    SqlDataReader dr2 = cmd2.ExecuteReader();
    dr2.Read();
    int assigned_id = dr2.GetInt32(0);

    con2.Close();  
    string value2 = "";
    for (int i = 0; i < DDLCount; i++)
    {

        DropDownList ddl = Panel4.FindControl("Text" + i) as DropDownList;
        value2 = ddl.SelectedValue.ToString();
        SqlConnection con = new SqlConnection("Data Source=ABC-0D30299B90A;Initial Catalog=JAPIT;Integrated Security=True");

        con.Open();

        SqlCommand cmd = new SqlCommand("insert into assign_deo values('" + assigned_id + "','" + value2 + "','" + DropDownList1.SelectedValue.ToString() + "')", con);


        cmd.ExecuteNonQuery();

        con.Close();

    }
    DropDownList1.ClearSelection();
    DropDownList2.ClearSelection();
    TextBox7.Text = "";
    TextBox2.Text = "";
    TextBox3.Text = "";
    TextBox4.Text = "";
    TextBox5.Text = "";
    TextBox6.Text = "";
    for (int i = 0; i < DDLCount; i++)
    {

        DropDownList ddl = Panel4.FindControl("Text" + i) as DropDownList;


        ddl.Dispose();

    }







}

Hi, I think it's great your posting your code but what exactly is wrong?

By that I mean are you getting an error message? Where is the message? Or what is supposed to happen and what actually happens?