Enter the three nos, need average of only two greater nos.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Data;

public partial class HomePage : System.Web.UI.Page
{
    adminDB admDB;
    protected void Page_Load(object sender, EventArgs e)
    {
        txtRegNo.Focus();
    }
    protected void btnSubmit_Click(object sender, EventArgs e)
    {
       

        //Retrive Marks
        try
        {
            DataSet ds = new DataSet();
            admDB = new adminDB();
            ds = admDB.RetriveIAMArks1(txtRegNo.Text, txtIA1.Text, ddlBranch.Text);
            if (ds.Tables[0].Rows.Count > 0)
            {
                lblmsg.Visible = false;
                gvNames.Visible = true;
                gvNames.DataSource = ds;
                gvNames.DataBind();
                lbl1.Text= ds.Tables[0].Rows[0][7].ToString();
            }
            else
            {
                gvNames.Visible = true;
                lblmsg.Text = "No results found!";
            }

            admDB = new adminDB();
            ds = admDB.RetriveIAMArks2(txtRegNo.Text, txtIA2.Text, ddlBranch.Text);
            if (ds.Tables[0].Rows.Count > 0)
            {
                lblmsg.Visible = false;
                gvNames.Visible = true;
                gvNames.DataSource = ds;
                gvNames.DataBind();
                lbl2.Text = ds.Tables[0].Rows[0][7].ToString();
            }
            else
            {
                gvNames.Visible = true;
                lblmsg.Text = "No results found!";
            }

            admDB = new adminDB();
            ds = admDB.RetriveIAMArks3(txtRegNo.Text, txtIA3.Text, ddlBranch.Text);
            if (ds.Tables[0].Rows.Count > 0)
            {
                lblmsg.Visible = false;
                gvNames.Visible = true;
                gvNames.DataSource = ds;
                gvNames.DataBind();
                lbl3.Text = ds.Tables[0].Rows[0][7].ToString();
            }
            else
            {
                gvNames.Visible = true;
                lblmsg.Text = "No results found!";
            }
        }
        catch (Exception ex)
        {
            lblmsg.Text = ex.ToString();
        }

        try
        {
            DataSet ds = new DataSet();
            admDB = new adminDB();
            ds = admDB.ViewAssignmentbyRegNo(txtRegNo.Text, ddlBranch.Text);
            if (ds.Tables[0].Rows.Count > 0)
            {
                lblmsg.Visible = false;
                gvNames.Visible = true;
                Label7.Visible = true;
                gvNames.DataSource = ds;
                gvNames.DataBind();

                int ia1, ia2, 1a3;
                decimal avg;
                ia1 = Convert.ToInt16(lbl1.Text);
                ia2 = Convert.ToInt16(lbl2.Text);
                
                avg = (ia1 + ia2 + ia3 ) / 2;
                lblavg.Text = avg.ToString();
            }
            else
            {
                lblmsg.Visible = true;
                gvNames.Visible = false;
                lblmsg.Text = "No results found!";
            }
        }
        catch (Exception ex)
        {
            lblmsg.Text = ex.ToString();
        }

    }
    protected void LinkButton1_Click(object sender, EventArgs e)
    {
        Response.Redirect("HomePage.aspx");
    }
}