How to get dropdownlist selected value in session

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C#

ASP.NET

After assigning ddl selected value in session for just to make sure checked session value in immediate window in run mode
But it didn't take ddl vale
session["id"]
The name 'session' does not exist in the current context

protected void btnsaveProduct_Click(object sender, EventArgs e)
    {

                  try
     {


con.Open();
       Label1.Text = DropDownList1.SelectedValue;
       Session["id"] = DropDownList1.SelectedValue;
        SqlCommand cmd = new SqlCommand("rsa_products_sp_ProductTable", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@Productname", txtProductName.Text);
        cmd.Parameters.AddWithValue("@ProductShortDescription", txtShortDescription.Text);
        cmd.Parameters.AddWithValue("@Productdescription", txtProductDescription.Text);
        cmd.Parameters.AddWithValue("@Price", txtPrice.Text);
        cmd.Parameters.AddWithValue("@MenuId", DropDownList1.SelectedItem.Value);>
     Please Help me with this.