Implementing Credit Limit

Question

I have created a webforms application for a micro-insurance business. In one of my forms, I added a button which redirects a user to page where he can sell insurance. Each user has a credit limit. Once reached, the idea is that the button which redirects to selling will be invisible. 

 

I was able to get the credit limit from the database. My problem is how can I hide or show the button if the condition is satisfied. Below is my design and snipets of my code behind. I'm still new in programming.

 

public partial class credit_limit : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            lblUserName.Text = Session["username"].ToString();
            lblDepartment.Text = Session["department"].ToString();

            if(!IsPostBack)
            {
                viewCreditLimit();
            }

        }

        protected void btnMotor_Click(object sender, EventArgs e)
        {

        }


        private void viewCreditLimit()
        {
            using (SqlConnection con = DBConn.GetDbCon())
            {
                con.Open();
                SqlCommand cmd = new SqlCommand("select CreditLimit from Login where UserName = @UserName and DepartmentID=@DepartmentID", con);
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.AddWithValue("@UserName", lblUserName.Text);
                cmd.Parameters.AddWithValue("@DepartmentID", lblDepartment.Text);

                using (SqlDataReader rdr = cmd.ExecuteReader())
                {
                    try
                    {
                        while (rdr.Read())
                        {
                            lblcreditlimit.Text = rdr["CreditLimit"].ToString();
                        }

                    }
                    catch(Exception ex)
                    {
                        throw ex;
                    }
                }

            }
        }

        private void showButton()
        {
            if (lblcreditlimit.Text < lblcreditlimit.Text)
            {
                Panel1.Visible = true;
            }
            else
            {
                Panel1.Visible = false;
                lblMessage.Text = "Your credit limit is already reached.";
            }
        }
    }