How do I write sql data into a textbox after a submit type event

Question

Finishing up some homework and Im having trouble with figuring out how to take information generated in sql column(a primary key set up to assign a record number to a customer example 1046) at submit and writing it to my redirected recipt page. I call it recipt.aspx. Any takers

Professor says to use a datareader...but things go bad after that.

public partial class _Default : System.Web.UI.Page
{
String cnStr = "EDITED FOR THE PURPOSE OF NOT DISPLAYED SQL SERVERta Source=111.11.111.11; uid=xxxxxxx; password=xxxx;    database=xxxxxx; ";
String insertStr;
SqlDataReader reader;
SqlConnection myConnection = new SqlConnection();


protected void submitbutton_Click(object sender, EventArgs e)
{               
    myConnection.ConnectionString = cnStr;
    try
    {
        //more magic happens as myConnection opens
        myConnection.Open();

        insertStr = "insert into connectAssignment values ('" + TextBox2.Text + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + bigtextthing.Text + "','" + DropDownList1.SelectedItem.Value + "')";

        //magic happens as Connection string is assigned to connection object and passes in the SQL statment
        //associate the command to the the myConnection connection object
        SqlCommand cmd = new SqlCommand(insertStr, myConnection);
        cmd.ExecuteNonQuery();
        Session["passmyvalue1"] = TextBox2.Text;
        Session["passmyvalue2"] = TextBox3.Text;
        Session["passmyvalue3"] = TextBox4.Text;
        Session["passmyvalue4"] = TextBox5.Text;
        Session["passmyvalue5"] = bigtextthing.Text; 
        Session["I NEED SOME HELP RIGHT HERE"] =Textbox6.Text;
        Response.Redirect("receipt.aspx");                 
    }
    catch
    {
        bigtextthing.Text =
            "Error submitting" + "Possible casues: Internet is down,server is down, check your settings!";
    }
    finally
    {
        myConnection.Close();
        TextBox2.Text = "";
        TextBox3.Text = "";
        TextBox4.Text = "";
        TextBox5.Text = "";
        bigtextthing.Text = "";
    }
    //reset validators?
}

The recipt page

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
   if(Session["passmyvalue1"] != null)   
   {   
    TextBox1.Text = (string)Session["passmyvalue1"];
    TextBox2.Text = (string)Session["passmyvalue2"];
    TextBox3.Text = (string)Session["passmyvalue3"];
    TextBox4.Text = (string)Session["passmyvalue4"];
    TextBox5.Text = (string)Session["passmyvalue5"]; 
    TextBox6.Text = I don't know ;
   }  
}
}

THanks for the help